Semiconductor chip assembly with precision-formed metal pillar

ABSTRACT

A semiconductor chip assembly includes a semiconductor chip that includes a conductive pad, a conductive trace that includes a routing line and a metal pillar, a connection joint that electrically connects the routing line and the pad, and an encapsulant. The metal pillar includes tapered sidewalls with first and second sidewall portions and a spike, and the first and second sidewall portions are concave arcs that are adjacent to one another at the spike.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.10/994,604 filed Nov. 22, 2004, now U.S. Pat. No. 7,129,575, which is acontinuation-in-part of U.S. application Ser. No. 10/922,280 filed Aug.19, 2004, now U.S. Pat. No. 7,009,297, which is a continuation-in-partof U.S. application Ser. No. 10/307,218 filed Nov. 29, 2002, now U.S.Pat. No. 6,809,414, which is a divisional of U.S. application Ser. No.09/997,973 filed Nov. 29, 2001, now U.S. Pat. No. 6,492,252, which is acontinuation-in-part of U.S. application Ser. No. 09/917,339 filed Jul.27, 2001, now U.S. Pat. No. 6,537,851, which is a continuation-in-partof U.S. application Ser. No. 09/878,626 filed Jun. 11, 2001, now U.S.Pat. No. 6,653,217, which is a continuation-in-part of U.S. applicationSer. No. 09/687,619 filed Oct. 13, 2000, now U.S. Pat. No. 6,440,835,each of which is incorporated by reference.

U.S. application Ser. No. 10/994,604 filed Nov. 22, 2004 also claims thebenefit of U.S. Provisional Application Ser. No. 60/523,566 filed Nov.20, 2003, which is incorporated by reference.

U.S. application Ser. No. 10/922,280 filed Aug. 19, 2004 also claims thebenefit of U.S. Provisional Application Ser. No. 60/497,672 filed Aug.25, 2003, and U.S. Provisional Application Ser. No. 60/497,425 filedAug. 22, 2003, each of which is incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor chip assembly, and moreparticularly to a semiconductor chip assembly with a metal pillar andits method of manufacture.

2. Description of the Related Art

Semiconductor chips have input/output pads that must be connected toexternal circuitry in order to function as part of an electronic system.The connection media is typically an array of metallic leads (e.g., alead frame) or a support circuit (e.g., a substrate), although theconnection can be made directly to a circuit panel (e.g., a motherboard). Several connection techniques are widely used. These includewire bonding, tape automated bonding (TAB) and flip-chip bonding.

Wire bonding is by far the most common and economical connectiontechnique. In this approach, wires are bonded, one at a time, from thechip to external circuitry by thermocompression, thermosonic orultrasonic processes. In thermocompression bonding, fine gold wire isfed from a spool through a clamp and a capillary. A thermal source isswept past an end of the wire to form a wire ball that protrudes fromthe capillary. The chip or capillary is then heated to about 200 to 300°C., the capillary is brought down over an aluminum pad, the capillaryexerts pressure on the wire ball, and the wire ball forms a ball bond onthe pad. The capillary is then raised and moved to a terminal on thesupport circuit, the capillary is brought down again, and thecombination of force and temperature forms a wedge bond between the wireand the terminal. Thus, the connection between the pad and the terminalincludes the ball bond (which only contacts the pad), the wedge bond(which only contacts the terminal) and the wire between the bonds. Afterraising the capillary again, the wire is ripped from the wedge bond, thethermal source is swept past the wire to form a new wire ball, and theprocess is repeated for other pads on the chip. Thermosonic bonding issimilar to thermocompression bonding but adds ultrasonic vibration asthe ball and wedge bonds are formed so that less heat is necessary.Ultrasonic bonding uses aluminum wire to form wedge bonds withoutapplying heat. There are many variations on these basic methods.

TAB involves bonding gold-bumped pads on the chip to external circuitryon a polymer tape using thermocompression bonding. TAB requiresmechanical force such as pressure or a burst of ultrasonic vibration andelevated temperature to accomplish metallurgical welding between thewires or bumps and the designated surface.

Flip-chip bonding involves providing pre-formed solder bumps on thepads, flipping the chip so that the pads face down and are aligned withand contact matching bond sites, and melting the solder bumps to wet thepads and the bond sites. After the solder reflows it is cooled down andsolidified to form solder joints between the pads and the bond sites.Organic conductive adhesive bumps with conductive fillers in polymerbinders have been used in place of solder bumps, but they do notnormally form a metallurgical interface in the classical sense. A majoradvantage of flip-chip bonding over wiring bonding and TAB is that itprovides shorter connection paths between the chip and the externalcircuitry, and therefore has better electrical characteristics such asless inductive noise, cross-talk, propagation delay and waveformdistortion. In addition, flip-chip bonding requires minimal mountingarea and weight which results in overall cost saving since no extrapackaging and less circuit board space are used.

While flip-chip technology has tremendous advantages over wire bondingand TAB, its cost and technical limitations are significant. Forinstance, the cost of forming bumps on the pads is significant. Inaddition, an adhesive is normally underfilled between the chip and thesupport circuit to reduce stress on the solder joints due to thermalmismatch between the chip and the support circuit, and the underfillingprocess increases both manufacturing complexity and cost.

Other techniques besides wire bonding, TAB and flip-chip technologieshave been developed to provide connection joints that electricallyconnect pads on chips to external conductive traces. These connectionjoints can be formed by electroplated metal, electrolessly plated metal,solder or conductive adhesive.

Electroplating provides deposition of an adherent metallic coating ontoa conductive object placed into an electrolytic bath composed of asolution of the salt of the metal to be plated. Using the terminal as ananode (possibly of the same metal as the one used for plating), a DCcurrent is passed through the solution affecting transfer of metal ionsonto the cathode surface. As a result, the metal continuallyelectroplates on the cathode surface. Electroplating using AC currenthas also been developed. Electroplating is relatively fast and easy tocontrol. However, a plating bus is needed to supply current whereelectroplating is desired. The plating bus creates design constraintsand must be removed after the electroplating occurs. Non-uniform platingmay arise at the bottom of relatively deep through-holes due to poorcurrent density distribution. Furthermore, the electrolytic bath isrelatively expensive.

Electroless plating provides metal deposition by an exchange reactionbetween metal complexes in a solution and a catalytic metal thatactivates or initiates the reaction. As a result, the electroless metalcontinually plates (i.e., deposits or grows) on the catalytic metal.Advantageously, the reaction does not require externally appliedelectric current. Therefore, electroless plating can proceed without aplating bus.

However, electroless plating is relatively slow. Furthermore, theelectroless bath is relatively expensive.

Solder joints are relatively inexpensive, but exhibit increasedelectrical resistance as well as cracks and voids over time due tofatigue from thermo-mechanical stresses. Further, the solder istypically a tin-lead alloy and lead-based materials are becoming farless popular due to environmental concerns over disposing of toxic ismaterials and leaching of toxic materials into ground water supplies.

Conductive adhesive joints with conductive fillers in polymer bindersare relatively inexpensive, but do not normally form a metallurgicalinterface in the classical sense. Moisture penetration through thepolymer binder may induce corrosion or oxidation of the conductivefiller particles resulting in an unstable electrical connection.Furthermore, the polymer binder and the conductive filler may degradeleading to an unstable electrical connection. Thus, the conductiveadhesive may have adequate mechanical strength but poor electricalcharacteristics.

Accordingly, each of these connection joint techniques has variousadvantages and disadvantages. The optimal approach for a givenapplication depends on design, reliability and cost considerations.

The semiconductor chip assembly is subsequently connected to anothercircuit such as a printed circuit board (PCB) or mother board duringnext level assembly.

Different semiconductor assemblies are connected to the next levelassembly in different ways. For instance, ball grid array (BGA) packagescontain an array of solder balls, and land grid array (LGA) packagescontain an array of metal pads that receive corresponding solder traceson the PCB.

Thermo-mechanical wear or creep of the solder joints that connect thesemiconductor chip assembly to the next level assembly is a major causeof failure in most board assemblies. This is because non-uniform thermalexpansion and/or contraction of different materials causes mechanicalstress on the solder joints. Thermal mismatch induced solder jointstress can be reduced by using materials having a similar coefficient ofthermal expansion (CTE). However, due to large transient temperaturedifferences between the chip and other materials during power-up of thesystem, the induced solder joint stress makes the assembly unreliableeven when the chip and the other materials have closely matched thermalexpansion coefficients.

Thermal mismatch induced solder joint stress can also be reduced byproper design of the support circuit. For instance, BGA and LGA packageshave been designed with pillar post type contact terminals that extendabove the package and act as a stand-off or spacer between the packageand the PCB in order to absorb thermal stress and reduce solder jointfatigue. The higher the aspect ratio of the pillar, the more easily thepillar can flex to follow expansion of the two ends and reduce shearstress.

Conventional approaches to forming the pillar either on a wafer or aseparate support circuit include a bonded interconnect process (BIP) andplating using photoresist.

BIP forms a gold ball on a pad of the chip and a gold pin extendingupwardly from the gold ball using a thermocompression wire bonder.Thereafter, the gold pin is brought in contact with a molten solder bumpon a support circuit, and the solder is reflowed and cooled to form asolder joint around the gold pin. A drawback to this approach is thatwhen the wire bonder forms the gold ball on the pad it appliessubstantial pressure to the pad which might destroy active circuitrybeneath the pad. In addition, gold from the pin can dissolve into thesolder to form a gold-tin intermetallic compound which mechanicallyweakens the pin and therefore reduces reliability.

U.S. Patent No. 5,722,162 discloses fabricating a pillar byelectroplating the pillar on a selected portion of an underlying metalexposed by an opening in photoresist and then stripping the photoresist.Although it is convenient to use photoresist to define the location ofthe pillar, electroplating the pillar in an opening in the photoresisthas certain drawbacks. First, the photoresist is selectively exposed tolight that initiates a reaction in regions of the photoresist thatcorrespond to the desired pattern. Since photoresist is not fullytransparent and tends to absorb the light, the thicker the photoresist,the poorer the penetration efficiency of the light. As a result, thelower portion of the photoresist might not receive adequate light toinitiate or complete the intended photo-reaction. Consequently, thebottom portion of the opening in the photoresist might be too narrow,causing a pillar formed in the narrowed opening to have a diameter thatdecreases with decreasing height. Such a pillar has a high risk offracturing at its lower portion in response to thermally induced stress.Furthermore, photoresist residue on the underlying metal might cause thepillar to have poor quality or even prevent the pillar from beingformed. Second, if the photoresist is relatively thick (such as 100microns or more), the photoresist may need to be applied with multiplecoatings and receive multiple light exposures and bakes, which increasescost and reduces yield. Third, if the photoresist is relatively thick,the electroplated pillar may be non-uniform due to poor current densitydistribution in the relatively deep opening. As a result, the pillar mayhave a jagged or pointed top surface instead of a flat top surface thatis better suited for providing a contact terminal for the next levelassembly.

In view of the various development stages and limitations in currentlyavailable semiconductor chip assemblies, there is a need for asemiconductor chip assembly that is cost-effective, reliable,manufacturable, versatile, provides a vertical conductor with excellentmechanical and electrical properties, and makes advantageous use theparticular connection joint technique best suited for a givenapplication.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a semiconductor chipassembly with a chip and a conductive trace that provides a low cost,high performance, high reliability package.

Another object of the present invention is to provide a convenient,cost-effective method for manufacturing a semiconductor chip assembly.

Generally speaking, the present invention provides a semiconductor chipassembly that includes a conductive pad, a conductive trace thatincludes a routing line and a metal pillar, a connection joint thatelectrically connects the routing line and the pad, and an encapsulant.The metal pillar includes tapered sidewalls with first and secondsidewall portions and a spike, and the first and second sidewallportions are concave arcs that are adjacent to one another at the spike.

Generally speaking, the present invention also provides a method ofmaking a semiconductor chip assembly that includes providing a metalbase, a routing line and a pillar etch mask that extends into a trench,mechanically attaching a semiconductor chip to the routing line, forminga connection joint that electrically connects the routing line and thepad, and etching the metal base to form a metal pillar with a tip.adjacent to the trench.

In accordance with an aspect of the invention, a semiconductor chipassembly includes (1) a semiconductor chip that includes first andsecond opposing surfaces, wherein the first surface of the chip includesa conductive pad, (2) a conductive trace that includes a routing lineand a metal pillar, wherein the metal pillar is a single-piece metal andincludes first and second opposing surfaces and tapered sidewallstherebetween, the first surface of the metal pillar faces in a firstdirection and contacts and is non-integral with the routing line, thesecond surface of the metal pillar faces in a second direction oppositethe first direction and is spaced from the routing line, the taperedsidewalls include first and second sidewall portions that are adjacentto one another at a spike in the metal pillar, the first sidewallportion is a concave arc that is adjacent to the first surface of themetal pillar, is spaced from the second surface of the metal pillar,slants inwardly towards the second surface of the metal pillar andextends vertically beyond the second sidewall portion in the firstdirection, the second sidewall portion is a concave arc that is adjacentto the second surface of the metal pillar, is spaced from the firstsurface of the metal pillar, slants inwardly towards the second surfaceof the metal pillar and extends vertically beyond the first sidewallportion in the second direction, and the spike protrudes laterally fromthe metal pillar and is spaced from the first and second surfaces of themetal pillar, (3) a connection joint that electrically connects therouting line and the pad, and (4) an encapsulant, wherein the chip isembedded in the encapsulant, the routing line extends laterally beyondthe metal pillar, and the metal pillar extends vertically beyond therouting line in the second direction, does not cover the routing line inthe second direction and is not covered in the second direction by theencapsulant or any other insulative material of the assembly.

The chip can be the only chip embedded in the encapsulant, oralternatively, multiple chips can be embedded in the encapsulant. Thefirst surface of the chip can face in the first direction and the secondsurface of the chip can face in the second direction, or alternatively,the first surface of the chip can face in the second direction and thesecond surface of the chip can face in the first direction. The chip canextend vertically beyond the routing line and the metal pillar in thefirst direction. The chip can also extend vertically beyond theconductive trace in the first direction. In addition, any chip embeddedin the encapsulant can extend vertically beyond the conductive trace inthe first direction.

The routing line can extend laterally beyond the metal pillar towardsthe chip. The routing line can extend or be disposed vertically beyondthe metal pillar in the first direction, and can extend or be disposedvertically beyond the chip in the second direction. The routing line canextend within and outside the periphery of the chip, or alternatively,be disposed outside the periphery of the chip. The routing line can alsobe essentially flat and parallel to the first and second surfaces of thechip. Furthermore, the routing line can be in an electrically conductivepath between the metal pillar and any chip embedded in the encapsulant.That is, any chip embedded in the encapsulant can be electricallyconnected to the metal pillar by an electrically conductive path thatincludes the routing line.

The metal pillar can extend or be disposed vertically beyond the chip,the routing line, the connection joint and the encapsulant in the seconddirection. The metal pillar can also be disposed within or outside theperiphery of the chip.

The metal pillar can have a generally conical shape with a diameter thatsubstantially continuously decreases from the first surface of the metalpillar to the second surface of the metal pillar as the metal pillarextends in the second direction.

The metal pillar can be copper or another metal that excludes solder.The second surface of the metal pillar can be flat and parallel to thefirst and second surfaces of the chip. Furthermore, the second surfaceof the metal pillar can be disposed within a surface area of the firstsurface of the metal pillar, and a surface area of the first surface ofthe metal pillar can be at least 20 percent larger than a surface areaof the second surface of the metal pillar.

The first sidewall portion can be a continuous concave arc, and thesecond sidewall portion can be a continuous concave arc. The firstsidewall portion can have a maximum diameter at the first surface of themetal pillar and a minimum diameter at the spike, and the secondsidewall portion can have a maximum diameter at the spike and a minimumdiameter at the second surface of the metal pillar. The first sidewallportion can extend vertically beyond the spike only in the firstdirection, and the second sidewall portion can extend vertically beyondthe spike only in the second direction, or alternatively, the secondsidewall portion can extend vertically beyond the spike in the first andsecond directions. The sidewalls can consist of the first and secondsidewall portions.

The spike can span 360 degrees laterally around the metal pillar and canprovide an abrupt discontinuity between the first and second sidewallportions. The spike can also be a first distance in the first directionfrom the first surface of the metal pillar and a second distance in thesecond direction from the second surface of the metal pillar, and thefirst distance can be greater than the second distance. For instance,the first distance can be at most four times the second distance, andmore particularly, the first distance can be about two times the seconddistance. In addition, the first and second distances can be constant asthe spike spans 360 degrees laterally around the metal pillar.

The connection joint can extend between and electrically connect therouting line and the pad. The connection joint can be electroplatedmetal, electrolessly plated metal, solder, conductive adhesive or a wirebond.

The encapsulant can contact the chip and the conductive trace and cancover the chip and the conductive trace in the first direction. Theencapsulant can also extend vertically beyond the chip, the routingline, the metal pillar and the connection joint in the first direction.

The assembly can include an insulative base that contacts the routingline and the metal pillar, is overlapped by the chip, extends verticallybeyond the chip, the routing line, the connection joint and theencapsulant in the second direction. The insulative base can also extendvertically beyond the spike in the second direction. The insulative basecan also extend vertically at least as far as the metal pillar in thesecond direction. For instance, the insulative base can extendvertically beyond the metal pillar in the second direction, oralternatively, the insulative base can be laterally aligned with themetal pillar at a surface that faces in the second direction. Inaddition, the metal pillar can be embedded in the insulative base, andthe chip and the encapsulant can extend vertically beyond the insulativebase in the first direction.

The assembly can include an insulative adhesive that contacts the chipand the encapsulant and extends vertically beyond the chip in the seconddirection.

The assembly can be a first-level package that is a single-chip ormulti-chip package.

In accordance with another aspect of the invention, a method of making asemiconductor chip assembly includes (1) providing a metal base, atrench, a routing line and a pillar etch mask, wherein the metal baseincludes first and second opposing surfaces, the trench extends into butnot through the metal base from the second surface of the metal basetowards the first surface of the metal base, is spaced from the firstsurface of the metal base and includes inner and outer peripheries thatare adjacent to the second surface of the metal base, the innerperiphery surrounds and is adjacent to a portion of the second surfaceof the metal base, the outer periphery surrounds and is spaced from theinner periphery, the routing line contacts the first surface of themetal base and is spaced from the trench, and the pillar etch maskextends into the trench and contacts and covers the portion of thesecond surface of the metal base, (2) mechanically attaching asemiconductor chip to the routing line, wherein the chip includes aconductive pad, (3) forming a connection joint that electricallyconnects the routing line and the pad, and (4) etching the metal baseusing a wet chemical etch, thereby reducing contact area between themetal base and the routing line and forming a metal pillar from anunetched portion of the metal base that contacts the routing line,wherein a portion of the first surface of the metal base forms a pillarbase of the metal pillar, the portion of the second surface of the metalbase forms a pillar tip of the metal pillar, the wet chemical etchremoves all of the metal base adjacent to the outer periphery, removesnone of the metal base adjacent to the inner periphery and forms thepillar base, and the pillar etch mask protects the pillar tip from thewet chemical etch.

The method can include forming an encapsulant that contacts and coversthe chip after attaching the chip to the routing line. The encapsulantcan be formed by transfer molding or curing.

The method can include forming an insulative base that covers therouting line and the metal pillar after forming the encapsulant, andthen removing a portion of the insulative base such that the insulativebase does not cover the pillar tip.

The method can include forming the routing line by selectivelydepositing the routing line on the metal base. For instance, the methodcan include forming a plating mask on the metal base, wherein theplating mask includes an opening that exposes a portion of the metalbase, and then electroplating the routing line on the exposed portion ofthe metal base through the opening in the plating mask.

The method can include forming the pillar etch mask by selectivelydepositing the pillar etch mask on the metal base. For instance, themethod can include forming a plating mask on the metal base, wherein theplating mask includes an opening that exposes a portion of the metalbase and exposes the trench, and then electroplating a metal layer onthe exposed portion of the metal base and the trench through the openingin the plating mask, wherein the pillar etch mask includes the metallayer.

The method can include forming the trench and the pillar etch mask byetching the metal base to form the trench and then depositing the pillaretch mask on the metal base and into the trench. For instance, themethod can include, in sequence, forming a trench etch mask on the metalbase, wherein the trench etch mask includes an opening that exposes aportion of the metal base, etching the metal base through the opening inthe trench etch mask, thereby forming the trench, removing the trenchetch mask, forming a plating mask on the metal base, wherein the platingmask includes an opening that exposes a portion of the metal base andexposes the trench, electroplating a metal layer on the exposed portionof the metal base and the trench through the opening in the platingmask, wherein the pillar etch mask includes the metal layer, andremoving the plating mask.

The method can include forming the trench, the routing line, and thepillar etch mask by, in sequence, forming a trench etch mask on themetal base, wherein the trench etch mask includes an opening thatexposes a portion of the metal base, etching the metal base through theopening in the trench etch mask, thereby forming the trench, removingthe trench etch mask, forming a first plating mask on the metal base,wherein the first plating mask includes a first opening that exposes afirst portion of the metal base, electroplating the routing line on thefirst exposed portion of the metal base through the first opening in thefirst plating mask, removing the first plating mask, forming a secondplating mask on the metal base, wherein the second plating mask includesa second opening that exposes a second portion of the metal base andexposes the trench, electroplating a metal layer on the second exposedportion of the metal base and the trench through the second opening inthe second plating mask, wherein the pillar etch mask includes the metallayer, and removing the second plating mask.

The method can include forming the trench and the metal pillar byetching the metal base using a first wet chemical etch, thereby formingthe trench and the pillar tip, then attaching the chip to the metalbase, the routing line and the metal layer, and then etching the metalbase using a second wet chemical etch, thereby forming the metal pillarand the pillar base.

The method can include attaching the chip to the routing line bydisposing an insulative adhesive between the chip and the metal base andthen hardening the adhesive.

The method can include forming the connection joint by plating theconnection joint between the routing line and the pad. For instance, theconnection joint can be electroplated or electrolessly plated betweenthe routing line and the pad. Alternatively, the method can includeforming the connection joint by depositing a non-solidified materialbetween the routing line and the pad and then hardening thenon-solidified material. For instance, solder paste can be depositedbetween the routing line and the pad and then hardened by reflowing, orconductive adhesive can be deposited between the routing line and thepad and then hardened by curing. Alternatively, the method can includeforming the connection joint by wire bonding.

The method can include etching the metal base to form the metal pillar,thereby exposing the routing line, removing most of the metal base,removing all of the metal base within the periphery of the pad, removingall of the metal base within the periphery of the chip, electricallyisolating the routing line from other routing lines that contact themetal base, and electrically isolating the pad from other pads of thechip. For instance, the method can include forming the connection jointby wire bonding, then forming the encapsulant, and then etching themetal base to form the metal pillar, thereby electrically isolating therouting line from the other routing lines and the pad from other pads.Alternatively, the method can include forming the encapsulant, thenforming the connection joint by electroplating using the metal base as aplating bus, and then etching the metal base to form the metal pillar,thereby electrically isolating the routing line from the other routinglines and the pad from the other pads. Alternatively, the method caninclude forming the encapsulant, then etching the metal base to form themetal pillar, thereby electrically isolating the routing line from theother routing lines, and then forming the connection joint byelectroless plating in which case the pad remains electrically isolatedfrom the other pads.

The method can include forming the trench to form the pillar tip and asecond sidewall portion of the metal pillar that is adjacent to thepillar tip and spaced from the first surface of the metal base, andetching the metal base to form the metal pillar, the pillar base and afirst sidewall portion of the metal pillar that is adjacent to thepillar base and the second sidewall portion and spaced from the pillartip without affecting the pillar tip and without affecting the secondsidewall portion.

The method can include forming the trench and then forming the routingline and the pillar etch mask. For instance, after forming the trench,the method can include forming the routing line and then forming thepillar etch mask, or alternatively, forming the pillar etch mask andthen forming the routing line, or alternatively, simultaneously formingthe routing line and the pillar etch mask.

The method can include forming the trench and then attaching the chip tothe metal base and the routing line. The method can also include formingthe trench and then forming the connection joint. For example, themethod can include attaching the chip to the metal base, the routingline and the pillar etch mask and then forming the connection joint. Asanother example, the method can include forming the trench, then formingthe routing line and the pillar etch mask, and then attaching the chipto the metal base, the routing line and the pillar etch mask and formingthe connection joint. In this example, the method can also includeattaching the chip to the metal base, the routing line and the pillaretch mask and then forming the connection joint as well as attaching thechip to the metal base, the routing line and the pillar etch mask andthen forming the metal pillar as well as forming the connection jointand then forming the metal pillar, or alternatively, forming the metalpillar and then forming the connection joint.

The method can include forming the connection joint and then forming themetal pillar, or alternatively, forming the metal pillar and thenforming the connection joint.

The method can include forming the connection joint and then forming theencapsulant, or alternatively, forming the encapsulant and then formingthe connection joint.

The method can include forming the metal pillar and then forming theencapsulant, or alternatively, forming the encapsulant and then formingthe metal pillar.

The method can include forming the encapsulant, then forming theconnection joint and then forming the metal pillar, or alternatively,forming the encapsulant, then forming the metal pillar and then formingthe connection joint.

The method can include or exclude removing the pillar etch mask afterforming the metal pillar.

The method can include (1) providing a metal base that includes firstand second opposing surfaces, then (2) etching the metal base using afirst wet chemical etch, thereby forming a trench in the metal base thatextends into but not through the metal base from the second surface ofthe metal base towards the first surface of the metal base, is spacedfrom the first surface of the metal base and includes inner and outerperipheries that are adjacent to the second surface of the metal base,wherein the inner periphery surrounds and is adjacent to a portion ofthe second surface of the metal base and the outer periphery surroundsand is spaced from the inner periphery, (3) forming a routing line onthe first surface of the metal base, wherein the routing line contactsthe first surface of the metal base and is spaced from the secondsurface of the metal base, (4) forming a metal layer on the secondsurface of the metal base, wherein the metal layer contacts the secondsurface of the metal base, is spaced from the first surface of the metalbase, extends into the trench and contacts and covers the portion of thesecond surface of the metal base, (5) mechanically attaching asemiconductor chip to the metal base and the routing line, wherein thechip includes a conductive pad, (6) forming a connection joint thatelectrically connects the routing line and the pad, and (7) etching themetal base using a second wet chemical etch after attaching the chip tothe metal base and the routing line and forming the metal layer, therebyreducing contact area between the metal base and the routing line andforming a metal pillar from an unetched portion of the metal base thatcontacts the routing line, wherein a portion of the first surface of themetal base forms a pillar base of the metal pillar, the portion of thesecond surface of the metal base forms a pillar tip of the metal pillar,the second wet chemical etch removes all of the metal base adjacent tothe outer periphery, removes none of the metal base adjacent to theinner periphery and forms the pillar base, and a pillar etch mask thatincludes the metal layer protects the pillar tip from the second wetchemical etch.

The method can include (1) providing a metal base, a trench, a routingline and a metal layer, wherein the metal base includes first and secondopposing surfaces, the first surface of the metal base faces in a firstdirection, the second surface of the metal base faces in a seconddirection opposite the first direction, the trench extends into but notthrough the metal base from the second surface of the metal base towardsthe first surface of the metal base, is spaced from the first surface ofthe metal base and includes inner and outer peripheries that areadjacent to the second surface of the metal base, the inner peripherysurrounds and is adjacent to a portion of the second surface of themetal base, the outer periphery surrounds and is spaced from the innerperiphery, the routing line contacts the first surface of the metal baseand is spaced from the trench, and the metal layer extends into thetrench and contacts and covers the portion of the second surface of themetal base, (2) mechanically attaching a semiconductor chip to the metalbase and the routing line, wherein the chip includes a conductive pad,(3) forming a connection joint that electrically connects the routingline and the pad, (4) forming an encapsulant after attaching the chip tothe metal base and the routing line, wherein the encapsulant contactsthe chip and extends vertically beyond the chip, the metal base and therouting line in the first direction, and the metal base extendsvertically beyond the chip and the routing line in the second direction,(5) etching the metal base using a wet chemical etch after forming themetal layer and the encapsulant, thereby reducing contact area betweenthe metal base and the routing line and forming a metal pillar from anunetched portion of the metal base that contacts the routing line andextends vertically beyond the chip and the routing line in the seconddirection, wherein a portion of the first surface of the metal baseforms a pillar base of the metal pillar, the portion of the secondsurface of the metal base forms a pillar tip of the metal pillar, thewet chemical etch removes all of the metal base adjacent to the outerperiphery, removes none of the metal base adjacent to the innerperiphery and forms the pillar base, and a pillar etch mask thatincludes the metal layer protects the pillar tip from the wet chemicaletch, then (6) forming an insulative base that covers the routing lineand the metal pillar and extends vertically beyond the chip, the routingline, the metal pillar, the connection joint and the encapsulant in thesecond direction, and then (7) removing a portion of the insulative basesuch that the insulative base does not cover the pillar tip in thesecond direction.

The method can include (1) providing a metal base that includes firstand second opposing surfaces, wherein the first surface of the metalbase faces in a first direction and the second surface of the metal basefaces in a second direction opposite the first direction, then (2)etching the metal base using a first wet chemical etch, thereby forminga trench in the metal base that extends into but not through the metalbase from the second surface of the metal base towards the first surfaceof the metal base, is spaced from the first surface of the metal baseand includes inner and outer peripheries that are adjacent to the secondsurface of the metal base, wherein the inner periphery surrounds and isadjacent to a portion of the second surface of the metal base and theouter periphery surrounds and is spaced from the inner periphery, (3)forming a routing line on the first surface of the metal base, whereinthe routing line contacts the first surface of the metal base and isspaced from the second surface of the metal base, (4) forming a metallayer on the second surface of the metal base, wherein the metal layercontacts the second surface of the metal base, is spaced from the firstsurface of the metal base, extends into the trench and contacts andcovers the portion of the second surface of the metal base, (5)mechanically attaching a semiconductor chip to the metal base and therouting line, wherein the chip includes a conductive pad, (6) forming aconnection joint that electrically connects the routing line and thepad, (7) forming an encapsulant after attaching the chip to the metalbase and the routing line, wherein the encapsulant contacts the chip andextends vertically beyond the chip, the metal base and the routing linein the first direction, and the metal base extends vertically beyond thechip, the routing line and the encapsulant in the second direction, (8)etching the metal base using a second wet chemical etch after formingthe metal layer and the encapsulant, thereby reducing contact areabetween the metal base and the routing line and forming a metal pillarfrom an unetched portion of the metal base that contacts the routingline and extends vertically beyond the chip, the routing line and theencapsulant in the second direction, wherein a portion of the firstsurface of the metal base forms a pillar base of the metal pillar, theportion of the second surface of the metal base forms a pillar tip ofthe metal pillar, the second wet chemical etch removes all of the metalbase adjacent to the outer periphery, removes none of the metal baseadjacent to the inner periphery and forms the pillar base, and a pillaretch mask that includes the metal layer protects the pillar tip from thesecond wet chemical etch, then (9) forming an insulative base thatcovers the routing line and the metal pillar and extends verticallybeyond the chip, the routing line, the metal pillar, the connectionjoint and the encapsulant in the second direction, and then (10)removing a portion of the insulative base such that the insulative basedoes not cover the pillar tip in the second direction.

The method can include attaching the chip to the metal base and therouting line (and, if already formed, the metal layer) by disposing aninsulative adhesive between the chip and the metal base and thenhardening the adhesive.

The method can include etching the metal base using the first wetchemical etch to form the pillar tip and a second sidewall portion ofthe metal pillar that is adjacent to the pillar tip and the trench andspaced from the first surface of the metal base, and etching the.metalbase using the second wet chemical etch to form the pillar base and afirst sidewall portion of the metal pillar that is adjacent to thepillar base and the second sidewall portion and spaced from the pillartip without affecting the pillar tip and without affecting the secondsidewall portion.

The method can include removing the portion of the insulative base bygrinding, laser ablation, plasma etching or photolithography.

The method can include removing the portion of the insulative base toexpose the pillar etch mask without exposing the metal pillar andwithout exposing the routing line. For instance, the method can includegrinding the insulative base without grinding the pillar etch mask andwithout grinding the metal pillar, then grinding the insulative base andthe pillar etch mask without grinding the metal pillar, and thendiscontinuing the grinding such that the insulative base is laterallyaligned with the pillar etch mask at a surface that faces in the seconddirection, the insulative base extends vertically beyond the metalpillar in the second direction and the metal pillar is unexposed.

The method can include removing the portion of the insulative base toexpose the metal pillar without exposing the routing line. For instance,the method can include grinding the insulative base without grinding themetal pillar, then grinding the insulative base and the metal pillar,and then discontinuing the grinding such that the insulative base islaterally aligned with the metal pillar at a surface that faces in thesecond direction and the metal pillar is exposed.

An advantage of the present invention is that the semiconductor chipassembly can be manufactured conveniently and cost effectively. Anotheradvantage is that the encapsulant can be provided before the metal baseis etched to form the metal pillar, thereby enhancing mechanical supportand protection for the routing line. Another advantage is that the metalpillar can be formed by etching (subtractively) rather than byelectroplating or electroless plating (additively) which improvesuniformity and reduces manufacturing time and cost. Another advantage isthat the metal pillar can be formed by a first wet chemical etch to formthe pillar tip and then a second wet chemical etch to form the pillarbase. In this manner, the pillar tip can be formed using a mildprecisely-controlled first wet chemical etch, and then the pillar basecan be formed using a coarse second wet chemical etch which the pillartip is protected from. Another advantage is that the connection jointcan be made from a wide variety of materials and processes, therebymaking advantageous use of mature connection joint technologies in aunique and improved manufacturing approach. Another advantage is thatthe assembly need not include wire bonds or TAB leads, although theprocess is flexible enough to accommodate these techniques if desired.Another advantage is that the assembly can be manufactured using lowtemperature processes which reduces stress and improves reliability. Afurther advantage is that the assembly can be manufactured usingwell-controlled processes which can be easily implemented by circuitboard, lead frame and tape manufacturers. Still another advantage isthat the assembly can be manufactured using materials that arecompatible with copper chip and lead-free environmental requirements.

These and other objects, features and advantages of the invention willbe further described and more readily apparent from a review of thedetailed description of the preferred embodiments which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description of the preferred embodiments can bestbe understood when read in conjunction with the following drawings, inwhich:

FIGS. 1A-25A are cross-sectional views showing a method of making asemiconductor chip assembly in accordance with a first embodiment of thepresent invention;

FIGS. 1B-25B are top plan views corresponding to FIGS. 1A-25A,respectively;

FIGS. 1C-25C are bottom plan views corresponding to FIGS. 1A-25A,respectively;

FIGS. 15D, 15E and 15F are enlarged cross-sectional, top and bottomviews, respectively, of an etch mask in the first embodiment;

FIGS. 20D, 20E and 20F are enlarged cross-sectional, top and bottomviews, respectively, of a metal pillar in the first embodiment;

FIGS. 24D, 24E and 24F are enlarged cross-sectional, top and bottomviews, respectively, of a contact terminal in the first embodiment;

FIGS. 26A, 26B and 26C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with asecond embodiment of the present invention;

FIGS. 27A, 27B and 27C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with athird embodiment of the present invention;

FIGS. 28A, 28B and 28C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with afourth embodiment of the present invention;

FIGS. 29A, 29B and 29C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with afifth embodiment of the present invention;

FIGS. 30A, 30B and 30C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with asixth embodiment of the present invention;

FIGS. 31A, 31B and 31C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with aseventh embodiment of the present invention;

FIGS. 32A, 32B and 32C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with aneighth embodiment of the present invention;

FIGS. 33A, 33B and 33C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with aninth embodiment of the present invention;

FIGS. 34A, 34B and 34C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with atenth embodiment of the present invention;

FIGS. 35A, 35B and 35C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with aneleventh embodiment of the present invention;

FIGS. 36A, 36B and 36C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with atwelfth embodiment of the present invention;

FIGS. 37A, 37B and 37C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with athirteenth embodiment of the present invention;

FIGS. 38A, 38B and 38C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with afourteenth embodiment of the present invention;

FIGS. 39A, 39B and 39C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with afifteenth embodiment of the present invention; and

FIGS. 40-44 are cross-sectional views of metal pillars in accordancewith a sixteenth to twentieth embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1A-25A, 1B-25B and 1C-25C are cross-sectional, top and bottomviews, respectively, of a method of making a semiconductor chip assemblyin accordance with a first embodiment of the present invention.

FIGS. 1A, 1B and 1C are cross-sectional, top and bottom views,respectively, of semiconductor chip 110 which is an integrated circuitin which various transistors, circuits, interconnect lines and the likeare formed (not shown). Chip 110 includes opposing major surfaces 112and 114 and has a thickness (between surfaces 112 and 114) of 150microns. Surface 112 is the active surface and includes conductive pad116 and passivation layer 118.

Pad 116 is substantially aligned with passivation layer 118 so thatsurface 112 is essentially flat. Alternatively, if desired, pad 116 canextend above or be recessed below passivation layer 118. Pad 116provides a bonding site to electrically couple chip 110 with externalcircuitry. Thus, pad 116 can be an input/output pad or a power/groundpad. Pad 116 has a length and width of 100 microns.

Pad 116 has an aluminum base that is cleaned by dipping chip 110 in asolution containing 0.05 M phosphoric acid at room temperature for 1minute and then rinsed in distilled water. Pad 116 can have the aluminumbase serve as a surface layer, or alternatively, pad 116 can be treatedto include a surface layer that covers the aluminum base, depending onthe nature of a connection joint that shall subsequently contact thesurface layer. In this embodiment, the connection joint is a gold wirebond. Therefore, pad 116 need not be treated to accommodate thisconnection joint. Alternatively, pad 116 can be treated by depositingseveral metal layers, such as chromium/copper/gold ortitanium/nickel/gold on the aluminum base. The chromium or titaniumlayer provides a barrier for the aluminum base and an adhesive betweenthe overlaying metal and the aluminum base. The metal layers, however,are typically selectively deposited by evaporation, electroplating orsputtering using a mask which is a relatively complicated process.Alternatively, pad 116 is treated by forming a nickel surface layer onthe aluminum base. For instance, chip 110 is dipped in a zinc solutionto deposit a zinc layer on the aluminum base. This step is commonlyknown as zincation. Preferably, the zinc solution contains about 150grams/liter of NaOH, 25 grams/liter of ZnO, and 1 gram/liter of NaNO₃,as well as tartaric acid to reduce the rate at which the aluminum basedissolves. Thereafter, the nickel surface layer is electrolesslydeposited on the zincated aluminum base. A suitable electroless nickelplating solution is Enthone Enplate NI-424 at 85° C.

Chip 110 includes many other pads on surface 112, and only pad 116 isshown for convenience of illustration. In addition, chip 110 has alreadybeen singulated from other chips that it was previously attached to on awafer.

FIGS. 2A, 2B and 2C are cross-sectional, top and bottom views,respectively, of metal base 120 which includes opposing major surfaces122 and 124. Metal base 120 is a copper plate with a thickness of 150microns.

FIGS. 3A, 3B and 3C are cross-sectional, top and bottom views,respectively, of photoresist layers 126 and 128 formed on metal base120. Photoresist layers 126 and 128 are deposited using a dry filmlamination process in which hot rolls simultaneously press photoresistlayers 126 and 128 onto surfaces 122 and 124, respectively. A reticle(not shown) is positioned proximate to photoresist layer 128.Thereafter, photoresist layer 128 is patterned by selectively applyinglight through the reticle, applying a developer solution to remove thephotoresist portion rendered soluble by the light, and then hard baking,as is conventional. As a result, photoresist layer 128 contains anopening that selectively exposes surface 124 of metal base 120, andphotoresist layer 126 remains unpatterned. Photoresist layers 126 and128 have a thickness of 25 microns beyond surfaces 122 and 124,respectively.

FIGS. 4A, 4B and 4C are cross-sectional, top and bottom views,respectively, of trench 130 formed in metal base 120.

Trench 130 is formed by applying a back-side wet chemical etch to theexposed portion of surface 124 using photoresist layer 128 as a trenchetch mask. For instance, a bottom spray nozzle (not shown) can spray thewet chemical etch on metal base 120 while a top spray nozzle (not shown)is deactivated, or the structure can be dipped in the wet chemical etchsince photoresist layer 126 provides front-side protection. The wetchemical etch is highly selective of copper and etches 50 microns intometal base 120. As a result, trench 130 extends from surface 124 intobut not through metal base 120.

Trench 130 includes inner periphery 130A at surface 124 and outerperiphery 130B at surface 124. Inner periphery 130A is surrounded by andspaced from outer periphery 130B. Trench 130 has an inner diameter of200 microns at inner periphery 130A, an outer diameter of 400 microns atouter periphery 130B, a width of 100 microns ((400-200)/2) between innerperiphery 130A and outer periphery 130B, a depth of 50 microns relativeto surface 124 and is spaced from surface 122 by 100 microns. Trench 130also has an annular shape at surface 124 (in a lateral plane orthogonalto the upward direction that surface 122 faces in and the downwarddirection that surface 124 faces in), a hemispherical cross-sectionalshape between surfaces 122 and 124 (in a vertical plane parallel to theupward and downward directions) and an overall donut shape.

Trench 130 defines inner surface portion 124A of surface 124. Inparticular, inner periphery 130A surrounds and is adjacent to innersurface portion 124A. That is, inner surface portion 124A is the entireportion of surface 124 encircled by inner periphery 130A. Thus, trench130 spans 360 degrees laterally around inner surface portion 124A, andinner surface portion 124A has a circular shape with a diameter of 200microns.

Trench 130 is also adjacent to outer surface portion 124B of surface124. In particular, outer periphery 130B is surrounded by and adjacentto outer surface portion 124B. That is, trench 130 is encircled by outersurface portion 124B. Thus, outer surface portion 124B spans 360 degreeslaterally around trench 130 and inner surface portion 124A, and isspaced from inner surface portion 124A by the width of trench 130. Outersurface portion 124B has an annular shape with an inner diameter of 400microns at outer periphery 130B, an outer diameter (not shown) of 450microns and a width of 25 microns ((450-400)/2).

A suitable wet chemical etch can be provided by a solution containingalkaline ammonia. The optimal etch time for exposing metal base 120 tothe wet chemical etch in order to form trench 130 with the desireddimensions can be established through trial and error.

FIGS. 5A, 5B and 5C are cross-sectional, top and bottom views,respectively, of metal base 120 after photoresist layers 126 and 128 arestripped. Photoresist layers 126 and 128 are removed using a solvent,such as a mild alkaline solution with a pH of 9, that is highlyselective of photoresist with respect to copper. Therefore, noappreciable amount of metal base 120 is removed.

FIGS. 6A, 6B and 6C are cross-sectional, top and bottom views,respectively, of photoresist layers 132 and 134 formed on metal base120. Photoresist layers 132 and 134 are deposited using a dry filmlamination process in which hot rolls simultaneously press photoresistlayers 132 and 134 onto surfaces 122 and 124, respectively. A reticle(not shown) is positioned proximate to photoresist layer 132.Thereafter, photoresist layer 132 is patterned by selectively applyinglight through the reticle, applying a developer solution to remove thephotoresist portion rendered soluble by the light, and then hard baking,as is conventional. As a result, photoresist layer 132 contains anopening that selectively exposes surface 122 of metal base 120, andphotoresist layer 134 remains unpatterned. Photoresist layers 132 and134 have a thickness of 50 microns beyond surfaces 122 and 124,respectively.

FIGS. 7A, 7B and 7C are cross-sectional, top and bottom views,respectively, of routing line 136 formed on metal base 120.

Routing line 136 contacts metal base 120 at surface 122 and is spacedfrom surface 124 and trench 130. Routing line 136 is composed of anickel layer electroplated on metal base 120 and a copper layerelectroplated on the nickel layer. The nickel layer contacts and issandwiched between metal base 120 and the copper layer, and the copperlayer contacts the nickel layer and is spaced from metal base 120. Thus,the nickel layer is buried beneath the copper layer, and the copperlayer is exposed. Routing line 136 has a thickness of 20 microns. Inparticular, the nickel layer has a thickness of 1 micron, and the copperlayer has a thickness of 19 microns. For convenience of illustration,the nickel and copper layers are shown as a single layer.

Routing line 136 is formed by an electroplating operation usingphotoresist layers 132 and 134 as plating masks. Thus, routing line 136is formed additively. Initially, a plating bus (not shown) is connectedto metal base 120, current is applied to the plating bus from anexternal power source, and metal base 120 is submerged in anelectrolytic nickel plating solution such as Technic Techni Nickel “S”at room temperature. As a result, the nickel layer electroplates(deposits or grows) on the exposed portions of metal base 120. Thenickel electroplating operation continues until the nickel layer has thedesired thickness. Thereafter, the structure is removed from theelectrolytic nickel plating solution and submerged in an electrolyticcopper plating solution such as Sel-Rex CUBATH M™ at room temperaturewhile current is applied to the plating bus to electroplate the copperlayer on the nickel layer. The copper electroplating operation continuesuntil the copper layer has the desired thickness. Thereafter, thestructure is removed from the electrolytic copper plating solution andrinsed in distilled water to remove contaminants.

Routing line 136 is a flat planar lead that includes elongated routingportion 138 and enlarged circular portion 140. Elongated routing portion138 and enlarged circular portion 140 are adjacent to and coplanar withone another. Elongated routing portion 138 has a width (orthogonal toits elongated length) of 100 microns, and enlarged circular portion 140has a diameter of 300 microns. Furthermore, elongated routing portion138 extends laterally from enlarged circular portion 140, and surfaceportion 124A and trench 130 are vertically aligned with enlargedcircular portion 140.

FIGS. 8A, 8B and 8C are cross-sectional, top and bottom views,respectively, of metal base 120 and routing line 136 after photoresistlayers 132 and 134 are stripped. Photoresist layers 132 and 134 areremoved using a solvent, such as a mild alkaline solution with a pH of9, that is highly selective of photoresist with respect to copper andnickel. Therefore, no appreciable amount of metal base 120 or routingline 136 is removed.

FIGS. 9A, 9B and 9C are cross-sectional, top and bottom views,respectively, of photoresist layers 142 and 144 formed on metal base120. Photoresist layers 142 and 144 are deposited in liquid form usingroller coating onto surfaces 122 and 124, respectively. A reticle (notshown) is positioned proximate to photoresist layer 142. Thereafter,photoresist layer 142 is patterned by selectively applying light throughthe reticle, applying a developer solution to remove the photoresistportion rendered soluble by the light, and then hard baking, as isconventional. As a result, photoresist layer 142 contains an openingthat selectively exposes routing line 136, and photoresist layer 144remains unpatterned. Photoresist layers 142 and 144 each have athickness of 50 microns beyond surfaces 122 and 124, respectively.

FIGS. 10A, 10B and 10C are cross-sectional, top and bottom views,respectively, of plated contact 146 formed on routing line 136.

Plated contact 146 contacts and is electrically connected to routingline 136, and is spaced from metal base 120. Plated contact 146 iscomposed of a nickel layer electroplated on routing line 136 and a goldlayer electroplated on the nickel layer. The nickel layer contacts andis sandwiched between routing line 136 and the gold layer, and the goldlayer contacts the nickel layer and is spaced from routing line 136.Thus, the nickel layer is buried beneath the gold layer, and the goldlayer is exposed. Plated contact 146 has a thickness of 3.5 microns. Inparticular, the nickel layer has a thickness of 3 microns, and the goldlayer has a thickness of 0.5 microns. For convenience of illustration,the nickel and gold layers are shown as a single layer.

Plated contact 146 is formed by an electroplating operation usingphotoresist layers 142 and 144 as plating masks. Thus, plated contact146 is formed additively. Initially, a plating bus (not shown) isconnected to metal base 120, current is applied to the plating bus froman external power source, and the structure is submerged in anelectrolytic nickel plating solution such as Technic Techni Nickel “S”at room temperature. As a result, the nickel layer electroplates on theexposed portion of routing line 136. The nickel electroplating operationcontinues until the nickel layer has the desired thickness. Thereafter,the structure is removed from the electrolytic nickel plating solutionand submerged in an electrolytic gold plating solution such as TechnicOrotemp at room temperature while current is applied to the plating busto electroplate the gold layer on the nickel layer. The goldelectroplating operation continues until the gold layer has the desiredthickness. Thereafter, the structure is removed from the electrolyticgold plating solution and rinsed in distilled water to removecontaminants.

FIGS. 11A, 11B and 11C are cross-sectional, top and bottom views,respectively, of metal base 120, routing line 136 and plated contact 146after photoresist layers 142 and 144 are stripped. Photoresist layers142 and 144 are removed using a solvent, such as a mild alkalinesolution with a pH of 9, that is highly selective of photoresist withrespect to copper, nickel and gold. Therefore, no appreciable amount ofmetal base 120, routing line 136 or plated contact 146 is removed.

FIGS. 12A, 12B and 12C are cross-sectional, top and bottom views,respectively, of photoresist layers 148 and 150 formed on metal base120. Photoresist layers 148 and 150 are deposited in liquid form usingroller coating onto surfaces 122 and 124, respectively. A reticle (notshown) is positioned proximate to photoresist layer 150.

Thereafter, photoresist layer 150 is patterned by selectively applyinglight through the reticle, applying a developer solution to remove thephotoresist portion rendered soluble by the light, and then hard baking,as is conventional. As a result, photoresist layer 150 contains anopening that fully exposes surface portions 124A and 124B and trench 130and is aligned with the outer diameter of outer surface portion 124B,and photoresist layer 148 remains unpatterned. Photoresist layers 148and 150 each have a thickness of 50 microns beyond surfaces 122 and 124,respectively.

FIGS. 13A, 13B and 13C are cross-sectional, top and bottom views,respectively, of metal layer 152 formed on metal base 120.

Metal layer 152 contacts metal base 120 at surface portions 124A and124B and trench 130 and is spaced from surface 122 and routing line 136.Metal layer 152 covers surface portions 124A and 124B and trench 130 inthe downward direction.

Furthermore, metal layer 152 is non-integral with metal base 120 andextends into but does not fill trench 130. Metal layer 152 is composedof solder and has a thickness of 5 microns.

Metal layer 152 is formed by an electroplating operation usingphotoresist layers 148 and 150 as plating masks. Thus, metal layer 152is formed additively. Initially, a plating bus (not shown) is connectedto metal base 120, current is applied to the plating bus from anexternal power source, and metal base 120 is submerged in anelectrolytic solder plating solution such as Technic Solder NF 72 BC atroom temperature. As a result, the solder layer electroplates on theexposed portions of metal base 120. The solder electroplating operationcontinues until the solder layer has the desired thickness. Thereafter,the structure is removed from the electrolytic solder plating solutionand rinsed in distilled water to remove contaminants.

Metal layer 152 is flat at surface portions 124A and 124B, is curved atand contours to trench 130, has a diameter of 450 microns and isvertically aligned with surface portions 124A and 124B, trench 130 andenlarged circular portion 140.

FIGS. 14A, 14B and 14C are cross-sectional, top and bottom views,respectively, of metal base 120, routing line 136, plated contact 146and metal layer 152 after photoresist layers 148 and 150 are stripped.Photoresist layers 148 and 150 are removed using a solvent, such as amild alkaline solution with a pH of 9, that is highly selective ofphotoresist with respect to copper, nickel, gold and solder. Therefore,no appreciable amount of metal base 120, routing line 136, platedcontact 146 or metal layer 152 is removed.

FIGS. 15A, 15B and 15C are cross-sectional, top and bottom views,respectively, of solder layer 154 formed on metal layer 152, and FIGS.15D, 15E and 15F are enlarged cross-sectional, top and bottom views,respectively, of etch mask 156.

Solder layer 154 contacts and is non-integral with metal layer 152 andis spaced from surface 122 and routing line 136. Solder layer 154 coversmetal layer 152 in the downward direction. Furthermore, solder layer 154extends into and fills the remaining space in trench 130. Solder layer154 has a thickness of 30 microns in the downward direction relative tosurface 124.

Solder layer 154 is formed by depositing solder paste on metal layer 152and then reflowing the solder paste. The solder paste includes finelypowdered tin-silver-copper solder particles mixed in a viscous organicresin containing a fluxing agent. The solder paste is deposited on metallayer 152 using stencil printing. During the stencil printing process, astencil (not shown) with a thickness of 100 microns is placed over metalbase 120, a stencil opening with a diameter of 400 microns is verticallyaligned with metal layer 152, and then a squeegee (not shown) pushes thesolder paste along the surface of the stencil opposite metal base 120,through the stencil opening and onto metal layer 152. The solder pasteis compliant enough at room temperature to conform to virtually anyshape. As a result, the solder paste fills the remaining space in trench130 and extends above trench 130 and metal layer 152 in the stencilopening. However, the solder paste contacts little or none of surface124.

Thereafter, the structure is heated to a temperature of about 260° C.The heat causes the flux in the solder paste to react with and removeoxides from metal layer 152 and the solder particles in the solderpaste, renders the solder particles in the solder paste molten such thatthey coalesce, and vaporizes the organic resin in the solder paste. As aresult, the solder paste contracts from its original size and solderreflow occurs. Although metal layer 152 is also solder, metal layer 152has a significantly higher melting point than 260° C. and remains solidduring the solder reflow. Furthermore, metal layer 152 provides awettable surface to facilitate the solder reflow, however metal base 120does not. As a result, the solder reflow is essentially confined tometal layer 152. Thereafter, the heat is removed and the molten solderparticles cool and solidify into solder layer 154 which is hardened.

Solder layer 154 has a diameter of 450 microns and is vertically alignedwith surface portions 124A and 124B, trench 130, enlarged circularportion 140 and metal layer 152.

Thus, metal layer 152 and solder layer 154 are deposited in sequence.That is, metal layer 152 is electroplated on metal base 120, and thensolder paste is deposited on metal layer 152 and then reflowed to formsolder layer 154.

Etch mask 156 is composed of metal layer 152 and solder layer 154. Etchmask 156 also includes body 160 and flange 162. Body 160 is the portionof etch mask 156 that is disposed outside trench 130, and flange 162 isthe portion of etch mask 156 that is disposed within trench 130. Thus,body 160 and flange 162 are vertically adjacent to one another and eachinclude portions of metal layer 152 and solder layer 154. In addition,etch mask 156, body 160 and flange 162 are solder.

Body 160 contacts surface portions 124A and 124B, covers and extendsdownwardly beyond surface portions 124A and 124B, trench 130 and flange162 and has a diameter of 450 microns. Body 160 includes solder surface160A that faces downwardly and is exposed.

Flange 162 contacts metal base 120 at trench 130, extends upwardlybeyond surface portions 124A and 124B and body 160, is spaced from anddoes not contact but is laterally aligned with and adjacent to surfaceportions 124A and 124B, and extends into and fills and assumes the shapeof trench 130. Flange 162 is proximate to but spaced from the peripheryof body 160 by a flat lateral surface of body 160 that covers outersurface portion 124B and has a width of 25 microns.

Flange 162 includes inner diameter 162A, outer diameter 162B, flangesurface 162C and flange tip 162D. Inner diameter 162A is identical toinner periphery 130A, and outer diameter 162B is identical to outerperiphery 130B. Thus, inner diameter 162A and outer diameter 162B areadjacent to surface portions 124A and 124B, respectively, and to body160, and are spaced from surface portions 124B and 124A, respectively,and from one another. Flange surface 162C faces upwardly, is a convexarc with substantially constant curvature as it extends laterally frominner diameter 162A to outer diameter 162B and includes flange tip 162Dat its apex. Flange surface 162C contacts and is covered by metal base120, is provided by metal layer 152 and is spaced from solder layer 154.Flange surface 162C includes inner surface portion 162E and outersurface portion 162F. Inner surface portion 162E is adjacent to innerdiameter 162A and spaced from outer diameter 162B, outer surface portion162F is adjacent to outer diameter 162B and spaced from inner diameter162A, and inner and outer surface portions 162E and 162F are adjacent toone another at circular boundary 162G (shown in phantom) between innerdiameter 162A and flange tip 162D. Flange tip 162D is the portion offlange 162 (and flange surface 162C) that extends farthest upwardly and(like trench 130) has a depth of 50 microns relative to surface 124 andis spaced from surface 122 by 100 microns.

Flange 162 has a diameter of 200 microns at inner diameter 162A, adiameter of 400 microns at outer diameter 162B, a width of 100 microns((400-200)/2) between inner diameter 162A and outer diameter 162B, adepth of 50 microns relative to surface 124 at flange tip 162D and isspaced from surface 122 by 100 microns at flange tip 162D. Flange 162also has an annular shape at surface 124 (in a lateral plane orthogonalto the upward and downward directions), a hemispherical cross-sectionalshape between surfaces 122 and 124 (in a vertical plane parallel to theupward and downward directions) and an overall donut shape.

For convenience of illustration, metal base 120 is shown above metallayer 152 and solder layer 154 to retain a single orientation throughoutthe figures for ease of comparison between the figures, although thestructure would be inverted during the formation of solder layer 154 sothat gravitational force would assist with the solder paste depositionand reflow.

FIGS. 16A, 16B and 16C are cross-sectional, top and bottom views,respectively, of adhesive 164 formed on metal base 120.

Adhesive 164 may include an organic surface protectant such as HK 2000which is promptly applied to the structure after photoresist layer 150is removed and solder layer 154 is formed to reduce native oxideformation on the exposed copper surfaces. The use of organic surfaceprotectant layers in insulative adhesives for semiconductor chipassemblies is well-known in the art.

Thereafter, a liquid resin (A stage) such as polyamic acid is appliedover metal base 120 using stencil printing. During stencil printing, astencil (not shown) is placed over metal base 120, routing line 136 andplated contact 146, a stencil opening is aligned with metal base 120 andoffset from routing line 136 and plated contact 146, and then a squeegee(not shown) pushes the liquid resin along the surface of the stencilopposite metal base 120, routing line 136 and plated contact 146,through the stencil opening and onto metal base 120 but not routing line136 and plated contact 146. The liquid resin is compliant enough at roomtemperature to conform to virtually any shape. Therefore, the liquidresin flows over and covers a portion of metal base 120 but remainsspaced from routing line 136 and plated contact 146.

FIGS. 17A, 17B and 17C are cross-sectional, top and bottom views,respectively, of chip 110 mechanically attached to metal base 120,routing line 136, plated contact 146 and etch mask 156 by adhesive 164.

Adhesive 164 contacts and extends between chip 110 and metal base 120but remains spaced from routing line 136 and plated contact 146. Surface112 of chip 110 faces upwardly and away from metal base 120 and isexposed, and surface 114 of chip 110 faces downwardly and towards metalbase 120 and is covered by adhesive 164. Chip 110 and metal base 120 donot contact one another, and chip 110 and routing line 136 do notcontact one another.

Adhesive 164 is sandwiched between chip 110 and metal base 120 usingrelatively low pressure from a pick-up head that places chip 110 onadhesive 164, holds chip 110 against adhesive 164 for 5 seconds and thenreleases chip 110. The pick-up head is heated to a relatively lowtemperature such as 150° C., and adhesive 164 receives heat from thepick-up head transferred through chip 110. As a result, adhesive 164proximate to chip 110 is partially polymerized (B stage) and forms a gelbut is not fully cured, and adhesive 164 that is partially polymerizedprovides a loose mechanical bond between chip 110 and metal base 120.

Chip 110 and metal base 120 are positioned relative to one another sothat chip 110 is disposed within the periphery of adhesive 164, androuting line 136, plated contact 146 and etch mask 156 are disposedoutside the periphery of chip 110. Chip 110 and metal base 120 can bealigned using an automated pattem recognition system.

Thereafter, the structure is placed in an oven and adhesive 164 is fullycured (C stage) at relatively low temperature in the range of 200 to250° C. to form a solid adhesive insulative thermosetting polyimidelayer that contacts and is sandwiched between and mechanically attacheschip 110 and metal base 120. Adhesive 164 is 30 microns thick betweenchip 110 and metal base 120.

At this stage, metal base 120 covers and extends downwardly beyond chip110, routing line 136, plated contact 146 and adhesive 164, routing line136 is disposed downwardly beyond and outside the periphery of chip 110and extends laterally beyond etch mask 156 towards chip 110, etch mask156 is disposed outside the periphery of chip 110 and extends downwardlybeyond chip 110, metal base 120, routing line 136 and plated contact146, and adhesive 164 extends downwardly beyond chip 110. Furthermore,chip 110 remains electrically isolated from routing line 136.

FIGS. 18A, 18B and 18C are cross-sectional, top and bottom views,respectively, of connection joint 166 formed on pad 116 and platedcontact 146.

Connection joint 166 is a gold wire bond that is ball bonded to pad 116and then wedge bonded to plated contact 146. The gold wire between theball bond and the wedge bond has a thickness of 25 microns. Thus,connection joint 166 contacts and electrically connects pad 116 andplated contact 146, and consequently, electrically connects pad 116 tometal base 120, routing line 136 and etch mask 156. Furthermore,connection joint 166 extends within and outside the periphery of chip110, extends upwardly beyond chip 110 by 100 microns and is spaced frommetal base 120, routing line 136 and etch mask 156.

FIGS. 19A, 19B and 19C are cross-sectional, top and bottom views,respectively, of encapsulant 168 formed on chip 110, routing line 136,plated contact 146, adhesive 164 and connection joint 166.

Encapsulant 168 is deposited by transfer molding. Transfer molding isthe most popular chip encapsulation method for essentially all plasticpackages. Generally speaking, transfer molding involves formingcomponents in a closed mold from a molding compound that is conveyedunder pressure in a hot, plastic state from a central reservoir calledthe transfer pot through a tree-like array of runners and gates intoclosed cavities. Molding compounds are well-known in the art.

The preferred transfer molding system includes a preheater, a mold, apress and a cure oven. The mold includes an upper mold section and alower mold section, also called “platens” or “halves” which define themold cavities. The mold also includes the transfer pot, runners, gatesand vents. The transfer pot holds the molding compound. The runners andgates provide channels from the transfer pot to the cavities. The gatesare placed near the entrances of the cavities and are constricted tocontrol the flow and injection velocity of the molding compound into thecavities and to facilitate removal of the solidified molding compoundafter molding occurs. The vents allow trapped air to escape but aresmall enough to permit only a negligible amount of the molding compoundto pass through them.

The molding compound is initially in tablet form. The preheater applieshigh-frequency energy to preheat the molding compound to a temperaturein the range of 50 to 100° C. The preheated temperature is below thetransfer temperature and therefore the preheated molding compound is notin a fluid state. In addition, the structure is placed in one of themold cavities, and the press operates hydraulically to close the moldand seal the mold cavities by clamping together the upper and lower moldsections. Guide pins ensure proper mating of the upper and lower moldsections at the parting line. In addition, the mold is heated to atransfer temperature in the range of 150 to 250° C. by insertingelectric heating cartridges in the upper and lower mold sections.

After closing the mold, the preheated molding compound in tablet form isplaced in the transfer pot. Thereafter, a transfer plunger appliespressure to the molding compound in the transfer pot. The pressure is inthe range of 10 to 100 kgf/cm² and preferably is set as high as possiblewithout introducing reliability problems. The combination of heat fromthe mold and pressure from the transfer plunger converts the moldingcompound in the transfer pot into a fluid state. Furthermore, thepressure from the transfer plunger forces the fluid molding compoundthrough the runners and the gates into the mold cavities. The pressureis maintained for a certain optimum time to ensure that the moldingcompound fills the cavities.

The lower mold section contacts and makes sealing engagement with and isgenerally flush with metal base 120. However, the upper mold section isspaced from connection joint 166 by 120 microns. As a result, themolding compound contacts the exposed portions of the chip 110, metalbase 120, routing line 136, plated contact 146, adhesive 164 andconnection joint 166 in the cavity. After 1 to 3 minutes at the transfertemperature, the molding compound polymerizes and is partially cured inthe mold.

Once the partially cured molding compound is resilient and hard enoughto withstand ejection forces without significant permanent deformation,the press opens the mold, ejector pins remove the molded structure fromthe mold, and excess molding compound attached to the molded structurethat solidified in the runners and the gates is trimmed and removed. Themolded structure is then loaded into a magazine and postcured in thecuring oven for 4 to 16 hours at a temperature somewhat lower than thetransfer temperature but well above room temperature to completely curethe molding compound.

The molding compound is a multi-component mixture of an encapsulatingresin with various additives. The principal additives include curingagents (or hardeners), accelerators, inert fillers, coupling agents,flame retardants, stress-relief agents, coloring agents and mold-releaseagents. The encapsulating resin provides a binder, the curing agentprovides linear/cross-polymerization, the accelerator enhances thepolymerization rate, the inert filler increases thermal conductivity andthermal shock resistance and reduces the thermal coefficient ofexpansion, resin bleed, shrinkage and residual stress, the couplingagent enhances adhesion to the structure, the flame retardant reducesflammability, the stress-relief agent reduces crack propagation, thecoloring agent reduces photonic activity and device visibility, and themold-release agent facilitates removal from the mold.

Encapsulant 168 contacts and covers chip 110, metal base 120, routingline 136, plated contact 146, adhesive 164 and connection joint 166.More particularly, encapsulant 168 contacts surface 112 and the outeredges of chip 110, but is spaced is from surface 114 of chip 110 (due toadhesive 164). Furthermore encapsulant 168 covers but is spaced frometch mask 156.

Encapsulant 168 is a solid adherent compressible protective layer thatprovides environmental protection such as moisture resistance andparticle protection for chip 110 as well as mechanical support forrouting line 136. Furthermore, chip 110 is embedded in encapsulant 168.

Encapsulant 168 extends upwardly beyond chip 110, routing line 136,plated contact 146, etch mask 156, adhesive 164 and connection joint166, has a thickness of 400 microns and extends 120 microns upwardlybeyond connection joint 166.

FIGS. 20A, 20B and 20C are cross-sectional, top and bottom views,respectively, of metal pillar 170 formed from metal base 120, and FIGS.20D, 20E and 20F are enlarged cross-sectional, top and bottom views,respectively, of metal pillar 170.

Metal pillar 170 is an unetched portion of metal base 120 that contactsand is non-integral with routing line 136 and is composed of copper.

Metal pillar 170 is formed by applying a wet chemical etch to metal base120 using etch mask 156 as a pillar etch mask to selectively protectmetal base 120. Thus, metal pillar 170 is an unetched portion of metalbase 120 defined by etch mask 156 that is formed subtractively.

A back-side wet chemical etch is applied to surface 124 of metal base120 and etch mask 156. For instance, the bottom spray nozzle can spraythe wet chemical etch on metal base 120 while the top spray nozzle isdeactivated, or the structure can be dipped in the wet chemical etchsince encapsulant 168 provides front-side protection. The wet chemicaletch is highly selective of copper with respect to nickel, solder,polyimide and the molding compound, and therefore, highly selective ofmetal base 120 with respect to the nickel layer of routing line 136,etch mask 156, adhesive 164 and encapsulant 168.

The wet chemical etch etches completely through metal base 120, therebyeffecting a pattern transfer of etch mask 156 onto metal base 120,exposing routing line 136 and adhesive 164, reducing but not eliminatingcontact area between metal base 120 and routing line 136, andeliminating contact area between metal base 120 and adhesive 164 andbetween metal base 120 and encapsulant 168. However, no appreciableamount of the nickel layer of routing line 136, etch mask 156, adhesive164 or encapsulant 168 is removed. Furthermore, the nickel layer ofrouting line 136 protects the underlying copper layer of routing line136 from the wet chemical etch. Therefore, no appreciable amount ofrouting line 136 is removed.

The wet chemical etch removes all of metal base 120 within the peripheryof chip 110 and removes most of metal base 120. The wet chemical etchalso removes all of outer surface portion 124B and none of inner surfaceportion 124A.

The wet chemical etch laterally undercuts metal base 120 relative toetch mask 156, causing metal pillar 170 to taper inwardly withincreasing height. A suitable taper is between 45 and slightly less than90 degrees, such as approximately 75 degrees. In particular, the wetchemical etch laterally undercuts metal base 120 relative to outersurface portion 162F, thereby removing all of metal base 120 thatcontacts outer surface portion 162F and exposing outer surface portion162F, however the wet chemical etch does not laterally undercut metalbase 120 relative to inner surface portion 162E, thereby removing noneof metal base 120 that contacts inner surface portion 162E which remainsunexposed.

Thus, the wet chemical etch removes outer surface portion 124B and allof metal base 120 that contacts outer surface portion 162F, however thewet chemical etch removes none of inner surface portion 124A or any ofmetal base 120 that contacts inner surface portion 162E since etch mask156 protects inner surface portion 124A and all of metal base 120 thatcontacts inner surface portion 162E from the wet chemical etch.Likewise, the wet chemical etch removes all of metal base 120 adjacentto outer periphery 130B, however the wet chemical etch removes none ofmetal base 120 adjacent to inner periphery 130A since etch mask 156protects all of metal base 120 adjacent to inner periphery 130A from thewet chemical etch. Etch mask 156 contacts and covers and extendsdownwardly beyond inner surface portion 124A, and inner surface portion124A remains unexposed. As a result, inner surface portion 124A is notexposed to or affected by the wet chemical etch and remains intact.Metal pillar 170 contacts routing line 136 at enlarged circular portion140, is spaced from elongated routing portion 138 and extends downwardlybeyond routing line 136. Thus, metal pillar 170 overlaps routing line136 in the downward direction, however metal pillar 170 does not coverrouting line 136 in the downward direction.

A suitable wet chemical etch can be provided by a solution containingalkaline ammonia. The optimal etch time for exposing metal base 120 tothe wet chemical etch in order to etch through metal base 120 and formmetal pillar 170 with the desired dimensions without excessivelyundercutting flange 162 or excessively exposing the nickel layer ofrouting line 136 to the wet chemical etch can be established throughtrial and error.

Metal pillar 170 includes pillar base 172, pillar tip 174, taperedsidewalls 176 and spike 178.

Pillar base 172 constitutes an unetched portion of surface 122 of metalbase 120, and pillar tip 174 is inner surface portion 124A whichconstitutes an unetched portion of surface 124 of metal base 120. Thus,pillar base 172 is formed using the wet chemical etch that forms metalpillar 170, and pillar tip 174 is formed using the wet chemical etchthat forms trench 130. Pillar base 172 faces upwardly, pillar tip 174faces downwardly, and pillar base 172 and pillar tip 174 are opposingsurfaces that are flat and parallel to surfaces 112 and 114 of chip 110,routing line 136 and one another. Pillar base 172 contacts and isnon-integral with and faces towards routing line 136 and is spaced fromand faces away from etch mask 156, and pillar tip 174 contacts and isnon-integral with and faces towards etch mask 156 and is spaced from andfaces away from routing line 136.

Tapered sidewalls 176 are adjacent to and extend between pillar base 172and pillar tip 174 and slant inwardly towards pillar tip 174. Taperedsidewalls 176 include base sidewall portion 176A and tip sidewallportion 176B. Base sidewall portion 176A is adjacent to pillar base 172,spaced from trench 130 and pillar tip 174 and extends upwardly beyondtip sidewall portion 176B and spike 178, tip sidewall portion 176B isadjacent to trench 130 and pillar tip 174, spaced from pillar base 172and extends downwardly beyond base sidewall portion 176A and spike 178,and sidewall portions 176A and 176B are adjacent to one another at spike178. Thus, base sidewall portion 176A is formed using the wet chemicaletch that forms metal pillar 170, and tip sidewall portion 176B isformed using the wet chemical etch that forms trench 130. Base sidewallportion 176A is a continuous concave arc that slants inwardly as itextends downwardly between pillar base 172 and spike 178 towards pillartip 174, has a maximum diameter at pillar base 172 and a minimumdiameter at spike 178, extends laterally beyond spike 178 only in theoutward direction and extends vertically beyond spike 178 only in theupward direction. Tip sidewall portion 176B is a continuous concave arcthat slants inwardly as it extends downwardly between spike 178 andpillar tip 174 towards pillar tip 174, has a maximum diameter at spike178 and a minimum diameter at pillar tip 174, extends laterally beyondspike 178 only in the inward direction and extends vertically beyondspike 178 only in the downward direction.

Spike 178 is the portion of metal pillar 170 at the boundary betweensidewall portions 176A and 176B. Thus, spike 178 is adjacent to sidewallportions 176A and 176B and spaced from pillar base 172 and pillar tip174. Spike 178 protrudes laterally as well as downwardly from metalpillar 170, spans 360 degrees laterally around metal pillar 170 at aconstant vertical distance between pillar base 172 and pillar tip 174and provides an abrupt discontinuity between sidewall portions 176A and176B. Spike 178 is spaced from pillar base 172 by a vertical distance of105 microns and is spaced from pillar tip 174 by a vertical distance of45 microns. Thus, spike 178 is disposed downwardly beyond flange tip162D by 5 microns (50-45) and is more than twice the vertical distancefrom pillar base 172 than from pillar tip 174. Furthermore, spike 178 islocated proximate to but spaced from flange tip 162D, between innerdiameter 162A and flange tip 162D, and therefore extends laterally anddownwardly slightly beyond flange tip 162D, is slightly closer thanflange tip 162D is to body 160, inner diameter 162A and pillar tip 174,and is slightly farther than flange tip 162D is to routing line 136,outer diameter 162B and pillar base 172.

Metal pillar 170 results from two sequential wet chemical etches. Pillartip 174 and tip sidewall portion 176B are formed using a first wetchemical etch that forms trench 130 and does not affect or form pillarbase 172 or base sidewall portion 176A, and then pillar base 172 andbase sidewall portion 176A are formed using a second wet chemical etchthat completes the formation of metal pillar 170 and does not affect orform pillar tip 174 or tip sidewall portion 176B. Moreover, since thefirst wet chemical etch only begins the formation of metal pillar 170,and the second wet chemical etch completes the formation of metal pillar170, the second wet chemical etch “forms” metal pillar 170.

Metal pillar 170 has a generally conical shape with a height (betweenpillar base 172 and pillar tip 174) of 150 microns and a diameter thatsubstantially continuously decreases as metal pillar 170 extendsdownwardly (from pillar base 172 to pillar tip 174). Pillar base 172 hasa circular shape with a diameter of 250 microns, and pillar tip 174 hasa circular shape with a diameter of 200 microns. Pillar base 172 andpillar tip 174 are vertically aligned with enlarged circular portion140, etch mask 156 and one another. Thus, pillar tip 174 isconcentrically disposed within the surface area of enlarged circularportion 140, etch mask 156 and pillar base 172. Furthermore, pillar base172 has a surface area that is at least 20 percent larger than thesurface area of pillar tip 174.

Metal pillar 170 is disposed outside the periphery of chip 110 andextends downwardly beyond chip 110, routing line 136, adhesive 164,connection joint 166 and encapsulant 168. Furthermore, chip 110 extendsupwardly beyond routing line 136, etch mask 156 and metal pillar 170,routing line 136 is disposed upwardly beyond etch mask 156 and metalpillar 170 and extends laterally beyond etch mask 156 and metal pillar170 towards chip 110, and encapsulant 168 covers and extends upwardlybeyond chip 110, routing line 136, etch mask 156, adhesive 164,connection joint 166 and metal pillar 170.

Encapsulant 168 provides mechanical support for routing line 136, etchmask 156 and metal pillar 170 and reduces mechanical strain on adhesive164, which is particularly useful after metal base 120 is etched to formmetal pillar 170. Encapsulant 168 protects routing line 136 and metalpillar 170 from mechanical damage by the wet chemical etch andsubsequent cleaning steps (such as rinsing in distilled water and airblowing). For instance, encapsulant 168 absorbs physical force of thewet chemical etch and cleaning steps that might otherwise separate chip110 and routing line 136. Thus, encapsulant 168 improves structuralintegrity and allows the wet chemical etch and subsequent cleaning stepsto be applied more vigorously, thereby improving manufacturingthroughput.

Conductive trace 180 includes routing line 136, plated contact 146, etchmask 156 and metal pillar 170. Conductive trace 180 is adapted forproviding horizontal and vertical routing between pad 116 and a nextlevel assembly.

FIGS. 21A, 21B and 21C are cross-sectional, top and bottom views,respectively, of insulative base 182 formed on routing line 136, etchmask 156, adhesive 164, encapsulant 168 and metal pillar 170.

Insulative base 182 is initially an epoxy in paste form that includes anepoxy resin, a curing agent, an accelerator and a filler. The filler isan inert material, such as silica (powdered fused quartz), that improvesthermal conductivity, thermal shock resistance, and thermal coefficientof expansion matching. The epoxy paste is blanketly deposited on routingline 136, etch mask 156, adhesive 164, encapsulant 168 and metal pillar170, and then the epoxy paste is cured or hardened at a relatively lowtemperature in the range of 100 to 250° C. to form a solid adherentinsulator that provides a protective seal for routing line 136 and metalpillar 170.

Insulative base 182 contacts and covers and extends downwardly beyondrouting line 136, etch mask 156, adhesive 164, encapsulant 168 and metalpillar 170, covers and extends downwardly beyond and is spaced from chip110, plated contact 146 and connection joint 166, and has a thickness of250 microns. Thus, insulative base 182 extends downwardly beyond routingline 136, etch mask 156 and metal pillar 170 and routing line 136, etchmask 156 and metal pillar 170 are unexposed.

For convenience of illustration, insulative base 182 is shown below chip110 to retain a single orientation throughout the figures for ease ofcomparison between the figures, although in this step the structurewould be inverted so that gravitational force would assist the epoxypaste deposition.

FIGS. 22A, 22B and 22C are cross-sectional, top and bottom views,respectively, of the structure after a lower portion of insulative base182 is removed.

The lower portion of insulative base 182 is removed by grinding. Inparticular, a rotating diamond sand wheel and distilled water areapplied to the back-side of insulative base 182. Initially, the diamondsand wheel grinds only insulative base 182. As the grinding continues,insulative base 182 becomes thinner as the grinded surface migratesupwardly. Eventually the diamond sand wheel contacts etch mask 156, andas a result, begins to grind solder layer 154 as well. As the grindingcontinues, solder layer 154 and insulative base 182 become thinner astheir grinded surfaces migrate upwardly. The grinding continues untilsolder layer 154 and insulative base 182 have the desired thickness, andthen halts before it reaches chip 110, routing line 136, plated contact146, metal layer 152, adhesive 164, connection joint 166 or encapsulant168. Thereafter, the structure is rinsed in distilled water to removecontaminants.

Solder layer 154 and insulative base 182 extend downwardly beyond metalpillar 170 by 20 microns after the grinding operation. Thus, thegrinding removes a 10 micron thick lower portion of solder layer 154 anda 30 micron thick lower portion of insulative base 182.

At this stage, chip 110 remains embedded in encapsulant 168, metalpillar 170 remains embedded in insulative base 182, routing line 136,metal layer 152 and metal pillar 170 remain unexposed, and solder layer154 is exposed. Insulative base 182 continues to contact and cover andextend downwardly beyond adhesive 164, cover and extend downwardlybeyond and be spaced from chip 110, plated contact 146 and connectionjoint 166, contact and extend downwardly beyond routing line 136,encapsulant 168 and metal pillar 170, and contact etch mask 156.Insulative base 182 also continues to overlap etch mask 156, encapsulant168 and metal pillar 170 in the downward direction, however insulativebase 182 no longer covers etch mask 156, encapsulant 168 or metal pillar170 in the downward direction. Thus, etch mask 156 is exposed androuting line 136 and metal pillar 170 remain unexposed. Furthermore,solder layer 154 and insulative base 182 are laterally aligned with oneanother at a surface that faces downwardly. Thus, an exposed planarizedhorizontal surface that faces downwardly includes solder layer 154 andinsulative base 182.

FIGS. 23A, 23B and 23C are cross-sectional, top and bottom views,respectively, of solder ball 184 formed on etch mask 156.

Solder ball 184 is initially a lead-free ball with a spherical shape anda diameter of 300 microns. The lead-free ball is dipped in flux toprovide solder ball 184 with a flux surface coating that surrounds thelead-free ball. Thereafter, the structure is inverted so that etch mask156 faces upwardly, and then solder ball 184 is deposited on etch mask156. Solder ball 184 weakly adheres to etch mask 156 due to the fluxsurface coating of solder ball 184.

For convenience of illustration, solder ball 184 is shown below etchmask 156 to retain a single orientation throughout the figures for easeof comparison between the figures, although the structure would beinverted during the deposition of solder ball 184 so that gravitationalforce would assist with the adhesion of solder ball 184 to etch mask156.

FIGS. 24A, 24B and 24C are cross-sectional, top and bottom views,respectively, of contact terminal 186 formed on metal pillar 170, andFIGS. 24D, 24E and 24F are enlarged cross-sectional, top and bottomviews, respectively, of contact terminal 186.

Contact terminal 186 includes metal layer 152 and solder layer 188, andsolder layer 188 is formed from solder layer 154 and solder ball 184.

Initially, solder ball 184 rests upon solder layer 154. Thereafter, thestructure is heated to a temperature of about 260° C. The heat causesthe flux in solder ball 184 to react with and remove oxides from solderlayer 154 and renders solder layer 154 and solder ball 184 molten. As aresult, solder layer 154 and solder ball 184 reflow together into amolten solder mixture and solder reflow occurs. Although metal layer 152is also solder, metal layer 152 has a significantly higher melting pointthan 260° C. and remains solid during the solder reflow. Furthermore,metal layer 152 provides a wettable surface to facilitate the solderreflow, however insulative base 182 does not. As a result, the solderreflow is essentially confined to metal layer 152. Thereafter, the heatis removed and the molten solder cools and solidifies into solder layer188 which is hardened. In this manner, solder layer 154 and solder ball184 are converted into solder layer 188.

Solder layer 188 has a diameter of 450 microns, a thickness of 50microns in the downward direction relative to insulative base 182 and isvertically aligned with enlarged circular portion 140, metal layer 152and metal pillar 170.

Thus, etch mask 156 and contact terminal 186 are formed in sequence.That is, metal layer 152 is electroplated on metal base 120, then solderpaste is deposited on metal layer 152 and then reflowed to form solderlayer 154 (thereby forming etch mask 156), then solder ball 184 isdeposited on solder layer 154, and then solder layer 154 and solder ball184 are reflowed together to form solder layer 188 (thereby formingcontact terminal 186).

Contact terminal 186 contacts and is non-integral with metal pillar 170and is spaced from routing line 136. In particular, contact terminal 186contacts pillar tip 174 and tip sidewall portion 176B, covers pillar tip174 and tip sidewall portion 176B in the downward direction and isspaced from pillar base 172 and base sidewall portion 176A.

Contact terminal 186 is composed of metal layer 152 and solder layer188. Contact terminal 186 also includes body 190 and flange 192. Body190 and flange 192 are identical to body 160 and flange 162,respectively, except that solder layer 188 replaces solder layer 154.Thus, body 190 and flange 192 are vertically adjacent to one another andeach include portions of metal layer 152 and solder layer 188 (ratherthan solder layer 154). In addition, contact terminal 186, body 190 andflange 192 are solder.

Body 190 contacts pillar tip 174 and insulative base 182, covers pillartip 174 and flange 192 in the downward direction, extends downwardlybeyond pillar tip 174, insulative base 182 and flange 192, is spacedfrom tip sidewall portion 176B, is embedded in insulative base 182, hasa diameter of 450 microns and includes solder surface 190A that facesdownwardly and is exposed. Body 190 is not covered in the downwarddirection by any material of the assembly. Furthermore, body 190 differsfrom body 160 in that body 190 extends downwardly beyond (rather thanlaterally aligned with) insulative base 182, and solder surface 190A hasa dome shape (rather than flat).

Flange 192 contacts metal pillar 170 and insulative base 182, contactsand covers and extends laterally beyond tip sidewall portion 176B,extends upwardly beyond pillar tip 174 and body 190, is spaced from anddoes not contact but is laterally aligned with and adjacent to pillartip 174, is embedded in insulative base 182 and is unexposed. Flange 192is proximate to but spaced from the periphery of body 190 by a flatlateral surface of body 190 that contacts insulative base 182 and has awidth of 25 microns, and is spaced from solder surface 190A.

Flange 192 has essentially identical size, shape and location as flange162. For instance, the wet chemical etch that forms metal pillar 170 andthe cure that hardens insulative base 182 may slightly affect the sizeof flange 162 but have no appreciable affect on flange 162. Likewise,the solder reflow operation that converts solder layer 154 and solderball 184 into solder layer 188 may slightly change the size of flange192 relative to flange 162 but has no appreciable affect on the size offlange 192 relative to flange 162. Thus, flange 192 has essentiallyidentical dimensions as flange 162. As a result, contact terminal 186includes flange 162 although the composition of flange 192 may differfrom the composition of flange 162.

Flange 192 includes inner diameter 192A, outer diameter 192B, flangesurface 192C and flange tip 192D, which correspond to and areessentially identical to inner diameter 162A, outer diameter 162B,flange surface 162C and flange tip 162D, respectively. Thus, innerdiameter 192A is essentially identical to inner periphery 130A, outerdiameter 192B is essentially identical to outer periphery 130B.Likewise, inner diameter 192A and outer diameter 192B are adjacent topillar tip 174 and insulative base 182, respectively, and to body 190,and are spaced from insulative base 182 and pillar tip 174,respectively, and from one another. Flange surface 192C faces upwardly,is a convex arc with substantially constant curvature as it extendslaterally from inner diameter 192A to outer diameter 192B and includesflange tip 192D at its apex. Flange surface 192C is provided by metallayer 152 and is spaced from solder layer 188.

Flange surface 192C includes inner surface portion 192E and outersurface portion 192F. Inner surface portion 192E is adjacent to innerdiameter 192A and spaced from outer diameter 192B, outer surface portion192F is adjacent to outer diameter 192B and spaced from inner diameter192A, and inner and outer surface portions 192E and 192F are adjacent toone another at circular boundary 192G (shown in phantom) that is betweeninner diameter 192A and flange tip 192D and coincides with circularboundary 162G and spike 178. Flange tip 192D is the portion of flange192 (and flange surface 192C) that extends farthest upwardly and (likeflange tip 162D) is vertically spaced from pillar tip 174 by 50 micronsand from pillar base 172 by 100 microns. Thus, flange tip 192D spans 360degrees laterally around metal pillar 170 at a constant verticaldistance between pillar base 172 and pillar tip 174.

Flange surface 192C provides an interlocking surface that contacts andis interlocked to metal pillar 170 and insulative base 182. Flangesurface 192C contacts metal pillar 170 adjacent to inner diameter 192Aand contacts insulative base 182 adjacent to outer diameter 192B. Inaddition, all of inner surface portion 192E contacts metal pillar 170,and all of outer surface portion 192F contacts insulative base 182.

Flange 192 has a diameter of 200 microns at inner diameter 192A, adiameter of 400 microns at outer diameter 192B, a width of 100 microns((400-200)/2) between inner diameter 192A and outer diameter 192B,extends upwardly by 50 microns relative to pillar tip 174 at flange tip192D and is spaced downwardly from pillar base 172 by 100 microns atflange tip 192D. Flange 192 also has an annular shape (in a lateralplane coplanar with pillar tip 174 and orthogonal to the upward anddownward directions), a hemispherical cross-sectional shape betweenpillar base 172 and pillar tip 174 (in a vertical plane parallel to theupward and downward directions) and an overall donut shape.

Contact terminal 186 contacts and is electrically connected to metalpillar 170 and extends downwardly beyond metal pillar 170 and insulativebase 182. Thus, contact terminal 186 is spaced from and extendsdownwardly beyond chip 110, routing line 136, plated contact 146,adhesive 164, connection joint 166 and encapsulant 168.

Moreover, contact terminal 186 provides a robust, permanent electricalconnection to metal pillar 170 that protrudes downwardly from metalpillar 170. Similarly, since contact terminal 186 is a permanent part ofthe assembly that includes metal layer 152 and solder layer 188, andsolder layer 188 is formed from solder layer 154 and solder ball 184,the assembly manufacture excludes removing etch mask 156.

At this stage, conductive trace 180 includes routing line 136, platedcontact 146, metal pillar 170 and contact terminal 186.

For convenience of illustration, solder layer 188 is shown below chip110 to retain a single orientation throughout the figures for ease ofcomparison between the figures, although the structure would be invertedduring the formation of solder layer 188 so that gravitational forcewould assist with the solder ball deposition and reflow.

FIGS. 25A, 25B and 25C are cross-sectional, top and bottom views,respectively, of the structure after cutting encapsulant 168 andinsulative base 182 with an excise blade to singulate the assembly fromother assemblies.

At this stage, the manufacture of semiconductor chip assembly 198 thatincludes chip 110, routing line 136, plated contact 146, adhesive 164,connection joint 166, encapsulant 168, metal pillar 170, insulative base182 and contact terminal 186 can be considered complete.

Chip 110 extends upwardly beyond conductive trace 180, overlapsinsulative base 182 in the upward direction but does not overlapconductive 180 in the upward direction. Thus, conductive trace 180 isdisposed outside the periphery of chip 110.

Routing line 136 is mechanically coupled to chip 110 by adhesive 164,and is electrically coupled to chip 110 by connection joint 166. Routingline 136 and connection joint 166 provide horizontal fan-out routingbetween pad 116 and external circuitry, and metal pillar 170 and contactterminal 186 provide vertical routing between pad 116 and externalcircuitry. Encapsulant 168 covers chip 110, connection joint 166,conductive trace 180 and insulative base 182 in the upward direction.Encapsulant 168 and insulative base 182 provide mechanical support andenvironmental protection for the assembly. Metal pillar 170 extendsdownwardly beyond but does not cover routing line 136 in the downwarddirection. Although metal pillar 170 is not exposed, and is overlappedby insulative base 182 and contact terminal 186 in the downwarddirection, metal pillar 170 is not covered in the downward direction byencapsulant 168, insulative base 182 or any other insulative material ofthe assembly. Furthermore, pillar tip 174 is not covered in the downwarddirection or even overlapped in the downward direction by encapsulant168, insulative base 182 or any other insulative material of theassembly.

Insulative base 182 contacts routing line 136, metal pillar 170 andcontact terminal 186, extends upwardly beyond contact terminal 186,extends downwardly beyond chip 110, routing line 136, connection joint166, encapsulant 168, metal pillar 170 and flange 192 but does notextend downwardly beyond body 190. Furthermore, insulative base 182contacts and covers base sidewall portion 176A and is spaced from tipsidewall portion 176B. Thus, insulative base 182 contacts and covers allof base sidewall portion 176A and is spaced from pillar base 172, pillartip 174 and tip sidewall portion 176B, and contact terminal 186 contactsand covers all of pillar tip 174 and tip sidewall portion 176B and isspaced from pillar base 172 and base sidewall portion 176A.

The semiconductor chip assembly is a single-chip first-level package.Thus, chip 110 is the only chip embedded in encapsulant 168.

The semiconductor chip assembly includes other conductive tracesembedded in encapsulant 168 and insulative base 182, and only a singleconductive trace 180 is shown for convenience of illustration. Theconductive traces are spaced and separated and electrically isolatedfrom one another. The conductive traces each include a respectiverouting line, plated contact, metal pillar and contact terminal. Theconductive traces are each electrically connected to a respective pad onchip 110 by a respective connection joint. The conductive traces eachprovide horizontal fan-out routing and vertical routing for theirrespective pads. Furthermore, the conductive traces each include adownwardly protruding contact terminal to provide a ball grid array(BGA) package.

Chip 110 is designed with the pads electrically isolated from oneanother. However, the corresponding routing lines are initiallyelectroplated on metal base 120 and electrically connected to oneanother by metal base 120. Furthermore, the connection jointselectrically connect the routing lines and the corresponding pads,thereby electrically connecting the pads with one another. Thereafter,once metal base 120 is etched to form the metal pillars, the routinglines are electrically isolated from one another, and therefore, thepads return to being electrically isolated from one another.

Advantageously, there is no plating bus or related circuitry that needbe disconnected or severed from the conductive traces after metal base120 is etched to form the metal pillars.

FIGS. 26A, 26B and 26C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with asecond embodiment of the present invention. In the second embodiment,the chip is flip-chip bonded. For purposes of brevity, any descriptionin the first embodiment is incorporated herein insofar as the same isapplicable, and the same description need not be repeated. Likewise,elements of the second embodiment similar to those in the firstembodiment have corresponding reference numerals indexed at two-hundredrather than one-hundred. For instance, chip 210 corresponds to chip 110,routing line 236 corresponds to routing line 136, etc.

Connection joint 266 is initially a solder bump deposited on pad 216.The solder bump has a hemispherical shape and a diameter of 100 microns.

Routing line 236 extends within and outside the periphery of chip 210.Thus, the elongated routing portion (corresponding to elongated routingportion 138) is lengthened. This is accomplished by a slight adjustmentto the electroplating operation previously described for routing line136. In particular, the photoresist layer (corresponding to photoresistlayer 132) is patterned to reshape the opening for routing line 236, andtherefore routing line 236 is lengthened relative to routing line 136.Furthermore, the plated contact (corresponding to plated contact 146) isomitted.

Chip 210 is positioned such that surface 212 faces downwardly, surface214 faces upwardly, routing line 236 extends laterally across pad 216,and connection joint 266 contacts and is sandwiched between pad 216 androuting line 236. Thereafter, heat is applied to reflow connection joint266, and then the heat is removed and connection joint 266 cools andsolidifies into a hardened solder joint that mechanically attaches andelectrically connects pad 216 and routing line 236. Connection joint 266exhibits localized wetting and does not collapse, and chip 210 remainsspaced from routing line 236.

Thereafter, adhesive 264 is dispensed into and underfills the open gapbetween chip 210 and the metal base (corresponding to metal base 120),and then adhesive 264 is cured. As a result, adhesive 264 contacts andis sandwiched between chip 210 and the metal base, contacts connectionjoint 266 and is spaced from pad 216. Thus, adhesive 264 issignificantly thicker than adhesive 164. A suitable underfill adhesiveis Namics U8443.

Thereafter, encapsulant 268, metal pillar 270, insulative base 282 andcontact terminal 286 are formed.

Semiconductor chip assembly 298 includes chip 210, routing line 236,adhesive 264, connection joint 266, encapsulant 268, metal pillar 270,insulative base 282 and contact terminal 286.

FIGS. 27A, 27B and 27C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with athird embodiment of the present invention. In the third embodiment, theconnection joint is electroplated. For purposes of brevity, anydescription in the first embodiment is incorporated herein insofar asthe same is applicable, and the same description need not be repeated.Likewise, elements of the third embodiment similar to those in the firstembodiment have corresponding reference numerals indexed atthree-hundred rather than one- hundred. For instance, chip 310corresponds to chip 110, routing line 336 corresponds to routing line136, etc.

Pad 316 is treated to accommodate an electroplated copper connectionjoint by forming a nickel surface layer on the aluminum base. Forinstance, chip 310 is dipped in a zinc solution to deposit a zinc layeron the aluminum base. This step is commonly known as zincation.Preferably, the zinc solution contains about 150 grams/liter of NaOH, 25grams/liter of ZnO, and 1 gram/liter of NaNO₃, as well as tartaric acidto reduce the rate at which the aluminum base dissolves. Thereafter, thenickel surface layer is electrolessly deposited on the zincated aluminumbase. A suitable electroless nickel plating solution is Enthone EnplateNI-424 at 85° C.

Routing line 336 extends within and outside the periphery of chip 310.Thus, the elongated routing portion (corresponding to elongated routingportion 138) is lengthened. This is accomplished by a slight adjustmentto the electroplating operation previously described for routing line136. In particular, the photoresist layer (corresponding to photoresistlayer 132) is patterned to reshape the opening for routing line 336, andtherefore routing line 336 is lengthened relative to routing line 136.

The metal base (corresponding to metal base 120) is etched to form aback-side recess (not shown), the plated contact (corresponding toplated contact 146) is omitted, and adhesive 364 is deposited on themetal base and routing line 336.

Chip 310 is inverted and positioned such that surface 312 facesdownwardly, surface 314 faces upwardly, adhesive 364 contacts and issandwiched between pad 316 and routing line 336, and routing line 336partially overlaps pad 316. Thereafter, encapsulant 368 is formed, andthen the metal base is etched again to convert the back-side recess intoa slot (not shown) that extends through the metal base, exposes adhesive364 and is vertically aligned with pad 316.

Thereafter, through-hole 365 is formed in adhesive 364 that exposes pad316. Through-hole 365 is formed by applying a suitable etch that ishighly selective of adhesive 364 with respect to pad 316 and routingline 336. In this instance, a selective is TEA CO₂ laser etch isapplied. The laser is directed at and vertically aligned with andcentered relative to pad 316. The laser has a spot size of 70 microns,and pad 316 has a length and width of 100 microns. As a result, thelaser strikes pad 316 and portions of routing line 336 and adhesive 364that extend within the periphery of pad 316, and ablates adhesive 364.The laser drills through and removes a portion of adhesive 364. However,portions of adhesive 364 that extend across the peripheral edges of pad316 are outside the scope of the laser and remain intact. Likewise,routing line 336 shields a portion of adhesive 364 from the laser etch,and a portion of adhesive 364 sandwiched between pad 316 and routingline 336 remains intact. The laser etch is anisotropic, and thereforelittle or none of adhesive 364 sandwiched between pad 316 and routingline 336 is undercut or removed. Through-hole 365 may slightly undercutadhesive 364 between pad 316 and routing line 336 and have a diameterthat is slightly larger than 70 microns due to the beam angle of thelaser, the thermal effects of the laser, and/or the isotropic nature ofan oxygen plasma or wet chemical cleaning step. For convenience ofexplanation, this slight undercut and enlargement is ignored. However,through-hole 365 is formed without damaging. chip 310 or routing line336 and does not extend into chip 310.

Thereafter, a brief cleaning step can be applied to remove oxides anddebris that may be present on the exposed portions of pad 316 androuting line 336. For instance, a brief oxygen plasma cleaning step canbe applied to the structure. Alternatively, a brief wet chemicalcleaning step using a solution containing potassium permanganate can beapplied to the structure. In either case, the cleaning step cleans theexposed portions of pad 316 and routing line 336 without damaging thestructure.

Thereafter, connection joint 366 is formed by an electroplatingoperation. Initially, the metal base is connected to a plating bus (notshown), current is applied to the plating bus from an external powersource, and the structure is submerged in an electrolytic copper platingsolution such as Sel-Rex CUBATH M™ at room temperature. As a result,connection joint 366 electroplates on the exposed portions of the metalbase. In addition, since the plating bus provides the current to themetal base, which in turn provides the current to routing line 336,connection joint 366 electroplates on the exposed portions of routingline 336 in through-hole 365. At the initial stage, since adhesive 364is an electrical insulator and pad 316 is not connected to the platingbus, connection joint 366 does not electroplate on pad 316 and is spacedfrom pad 316. However, as the copper electroplating continues,connection joint 366 continues to plate on routing line 336, extendsthrough adhesive 364 and contacts pad 316. As a result, pad 316 isconnected to the plating bus by the metal base, routing line 336 andconnection joint 366, and therefore connection joint 366 begins toelectroplate on pad 316 as well. The copper electroplating continuesuntil connection joint 366 has the desired thickness. Thereafter, thestructure is removed from the electrolytic copper plating solution andrinsed in distilled water to remove contaminants.

Thereafter, insulative plug 369 is formed on adhesive 364 and connectionjoint 366 and disposed within the slot, and then metal pillar 370,insulative base 382 and contact terminal 386 are formed.

Semiconductor chip assembly 398 includes chip 310, routing line 336,adhesive 364, connection joint 366, encapsulant 368, insulative plug369, metal pillar 370, insulative base 382 and contact terminal 386.

FIGS. 28A, 28B and 28C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with afourth embodiment of the present invention. In the fourth embodiment,the connection joint is electrolessly plated. For purposes of brevity,any description in the first embodiment is incorporated herein insofaras the same is applicable, and the same description need not berepeated. Likewise, elements of the fourth embodiment similar to thosein the first embodiment have corresponding reference numerals indexed atfour-hundred rather than one- hundred. For instance, chip 410corresponds to chip 110, routing line 436 corresponds to routing line136, etc.

Pad 416 is treated to include a nickel surface layer in the same manneras pad 316, routing line 436 is configured in the same manner as routingline 336, adhesive 464 is deposited on the metal base (corresponding tometal base 120) and routing line 436 in the same manner that adhesive364 is deposited on the metal base and routing line 336, and the platedcontact (corresponding to plated contact 146) is omitted.

Chip 410 is inverted and positioned such that surface 412 facesdownwardly, surface 414 faces upwardly, adhesive 464 contacts and issandwiched between pad 416 and routing line 436, and routing line 436partially overlaps pad 416. Thereafter, encapsulant 468 is formed, andthen the metal base is etched to form metal pillar 470. Thereafter,through-hole 465 is formed in adhesive 464 and exposes pad 416.Through-hole 465 is formed in the same manner as through-hole 365.

Thereafter, connection joint 466 is formed by an electroless platingoperation. The structure is submerged in an electroless nickel platingsolution such as Enthone Enplate NI-424 at 85° C. Preferred nickelplating solutions include nickel-sulfate and nickel-chloride and have apH of about 9.5 to 10.5. A higher nickel concentration provides a fasterplating rate but reduces the stability of the solution. The amount ofchelating agents or ligands in the solution depends on the nickelconcentration and their chemical structure, functionality and equivalentweight. Most of the chelating agents used in electroless nickel platingsolutions are hydroxy organic acids which form one or more water solublenickel ring complexes. These complexes reduce the free nickel ionconcentration, thereby increasing the stability of the solution whileretaining a reasonably fast plating rate. Generally, the higher thecomplex agent concentration, the slower the plating rate. In addition,the pH of the solution and the plating rate continually decrease as theelectroless plating continues due to hydrogen ions being introduced intothe solution as a byproduct of the nickel reduction. Accordingly, thesolution is buffered to offset the effects of the hydrogen ions.Suitable buffering agents include sodium or potassium salts of mono anddibasic organic acids. Finally, those skilled in the art will understandthat electroless nickel plating solutions do not deposit pure elementalnickel since a reducing agent such as H₂PO₂ will naturally decomposeinto the electrolessly plated nickel. Therefore, those skilled in theart will understand that electrolessly plated nickel refers to a nickelcompound that is mostly nickel but not pure elemental nickel.

Pad 416 includes an exposed nickel surface layer and therefore iscatalytic to electroless nickel. Furthermore, adhesive 464 andencapsulant 468 are not catalytic to electroless nickel and therefore aplating mask is not necessary. Connection joint 466 plates on pad 416and eventually contacts and electrically connects pad 416 and routingline 436 in through-hole 465. The electroless nickel plating operationcontinues until connection joint 466 is about 10 microns thick.Thereafter, the structure is removed from the electroless nickel platingsolution and rinsed in distilled water.

Thereafter, insulative base 482 and contact terminal 486 are formed.

Semiconductor chip assembly 498 includes chip 410, routing line 436,adhesive 464, connection joint 466, encapsulant 468, metal pillar 470,insulative base 482 and contact terminal 486.

FIGS. 29A, 29B and 29C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with afifth embodiment of the present invention. In the fifth embodiment, thepillar etch mask provides the contact terminal. For purposes of brevity,any description in the first embodiment is incorporated herein insofaras the same is applicable, and the same description need not berepeated. Likewise, elements of the fifth embodiment similar to those inthe first embodiment have corresponding reference numerals indexed atfive-hundred rather than one-hundred. For instance, chip 510 correspondsto chip 110, routing line 536 corresponds to routing line 136, etc.

The solder ball (corresponding to solder ball 184) is omitted, andtherefore the solder layer (corresponding to solder layer 188) is alsoomitted. As a result, etch mask 556 provides contact terminal 586.Contact terminal 586 consists of metal layer 552 and solder layer 554,and insulative base 582 and contact terminal 586 and are laterallyaligned with one another at a surface that faces downwardly. Thus, anexposed planarized horizontal surface that faces downwardly includessolder layer 554 and insulative base 582, and solder layer 554 providessolder surface 590A that is flat (rather than dome shaped). Furthermore,the conductive traces each include a laterally aligned (rather thandownwardly protruding) contact terminal to provide a land grid array(LGA) package.

Semiconductor chip assembly 598 includes chip 510, routing line 536,plated contact 546, adhesive 564, connection joint 566, encapsulant 568,metal pillar 570, insulative base 582 and contact terminal 586.

FIGS. 30A, 30B and 30C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with asixth embodiment of the present invention. In the sixth embodiment, thecontact terminal provides the pillar etch mask. For purposes of brevity,any description in the first embodiment is incorporated is hereininsofar as the same is applicable, and the same description need not berepeated. Likewise, elements of the sixth embodiment similar to those inthe first embodiment have corresponding reference numerals indexed atsix-hundred rather than one-hundred. For instance, chip 610 correspondsto chip 110, routing line 636 corresponds to routing line 136, etc.

The solder ball (corresponding to solder ball 184) is deposited on theetch mask (corresponding to etch mask 156) after encapsulant 668 isformed. Thereafter, the solder ball and the solder layer (correspondingto solder layer 154) are reflowed together to form contact terminal 686.Thereafter, the metal base (corresponding to metal base 120) is etchedto form metal pillar 670.

Insulative base 682 is formed without a filler. As a result, insulativebase 682 is more susceptible to plasma etching than insulative base 182.The grinding operation is omitted, and instead a blanket back-sideplasma etch is applied to the structure. The plasma etch is highlyselective of epoxy with respect to solder, and therefore, highlyselective of insulative base 682 with respect to contact terminal 686.The plasma etch removes an 80 micron thick lower portion of insulativebase 682. As a result, contact terminal 686 protrudes from and extendsdownwardly beyond insulative base 682, and insulative base 682 isrecessed relative to contact terminal 686 in the downward direction.Furthermore, insulative base 682 extends downwardly beyond metal pillar670, and metal pillar 670 remains unexposed.

Semiconductor chip assembly 698 includes chip 610, routing line 636,plated contact 646, adhesive 664, connection joint 666, encapsulant 668,metal pillar 670, insulative base 682 and contact terminal 686.

FIGS. 31A, 31B and 31C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with aseventh embodiment of the present invention. In the seventh embodiment,the portion of the insulative base is removed by laser ablation. Forpurposes of brevity, any description in the first embodiment isincorporated herein insofar as the same is applicable, and the samedescription need not be repeated. Likewise, elements of the seventhembodiment similar to those in the first embodiment have correspondingreference numerals indexed at seven-hundred rather than one-hundred. Forinstance, chip 710 corresponds to chip 110, routing line 736 correspondsto routing line 136, etc.

Insulative base 782 is formed without a filler. As a result, insulativebase 782 is more susceptible to laser etching than insulative base 182.The grinding operation is omitted, and instead a selective TEA CO₂ laseretch is applied using multiple laser direct writes. The laser isdirected at the etch mask (corresponding to etch mask 156). The laserhas a spot size of 100 microns. Furthermore, the laser direct writes areoffset relative to one another yet overlap so that the laser scans acentral portion of the etch mask with a diameter of 150 microns. In thismanner, the laser direct writes in combination are vertically alignedwith and centered relative to the etch mask and metal pillar 770. As aresult, the laser strikes the etch mask, a portion of insulative base782 that overlaps the etch mask, and ablates insulative base 782.

The laser drills through and removes a portion of insulative base 782.However, a portion of insulative base 782 that extends across theperiphery of the etch mask is outside the scope of the laser and remainsintact. Thus, insulative base 782 continues to contact and overlap butno longer covers the etch mask.

Thereafter, a brief cleaning step can be applied to remove oxides anddebris that may be present on the exposed portion of the etch mask. Forinstance, a brief oxygen plasma cleaning step can be applied to thestructure. Alternatively, a brief wet chemical cleaning step using asolution containing potassium permanganate can be applied to thestructure. In either case, the cleaning step cleans the exposed portionof the etch mask without damaging the structure.

Opening 783 is formed in and extends vertically into but not throughinsulative base 782, is disposed outside the periphery of chip 710, isvertically aligned with the etch mask and metal pillar 770, exposes theetch mask, is spaced from routing line 736, adhesive 764, encapsulant768 and metal pillar 770 and has a diameter of 150 microns. Opening 783is formed without damaging or extending into the etch mask.

Opening 783 may have a diameter that is slightly larger than 150 micronsdue to the beam angle of the laser, the thermal effects of the laser,and/or the isotropic nature of an oxygen plasma or wet chemical cleaningstep. For convenience of explanation, this slight enlargement isignored.

Thereafter, contact terminal 786 is formed. Contact terminal 786 extendswithin and outside and fills opening 783 and extends downwardly beyondinsulative base 782. Insulative base 782 does not cover pillar tip 774in the downward direction, however insulative base 782 overlaps pillartip 774 in the downward direction and metal pillar 770 remainsunexposed.

Semiconductor chip assembly 798 includes chip 710, routing line 736,plated contact 746, adhesive 764, connection joint 766, encapsulant 768,metal pillar 770, insulative base 782 and contact terminal 786.

FIGS. 32A, 32B and 32C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with aneighth embodiment of the present invention. In the eighth embodiment,the insulative base is omitted. For purposes of brevity, any descriptionin the first embodiment is incorporated herein insofar as the same isapplicable, and the same description need not be repeated. Likewise,elements of the eighth embodiment similar to those in the firstembodiment have corresponding reference numerals indexed ateight-hundred rather than one- hundred. For instance, chip 810corresponds to chip 110, routing line 836 corresponds to routing line136, etc.

The insulative base (corresponding to insulative base 182) is omitted,and therefore the grinding operation is unnecessary.

Semiconductor chip assembly 898 includes chip 810, routing line 836,plated contact 846, adhesive 864, connection joint 866, encapsulant 868,metal pillar 870 and contact terminal 886.

FIGS. 33A, 33B and 33C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with aninth embodiment of the present invention. In the ninth embodiment, thepillar etch mask is removed. For purposes of brevity, any description inthe first embodiment is incorporated herein insofar as the same isapplicable, and the same description need not be repeated.

Likewise, elements of the ninth embodiment similar to those in the firstembodiment have corresponding reference numerals indexed at nine-hundredrather than one-hundred. For instance, chip 910 corresponds to chip 110,routing line 936 corresponds to routing line 136, etc.

Routing line 936 and the etch mask (corresponding to metal layer 152)are simultaneously formed during an electroplating operation. This isaccomplished by a slight adjustment to the electroplating operationpreviously described for routing line 136. In particular, thephotoresist layer (corresponding to photoresist layer 134) is patternedlike the photoresist layer (corresponding to photoresist layer 150) forthe metal layer (corresponding to metal layer 152). As a result, routingline 936 and the etch mask are each composed of a nickel layerelectroplated on the metal base (corresponding to metal base 120) and acopper layer electroplated on the nickel layer. In both routing line 936and the etch mask, the nickel layer contacts and is sandwiched betweenthe metal base and the copper layer, is buried beneath the copper layerand has a thickness of 1 micron, and the copper layer contacts thenickel layer, is spaced from the metal base, is exposed and has athickness of 19 microns. In addition, the photoresist layers(corresponding to photoresist layers 148 and 150) and relatedelectroplating operation are omitted, and the subsequent solder pastedeposition and reflow operations are omitted. As a result, the solderlayer (corresponding to solder layer 154) is omitted.

Thereafter, adhesive 964 is formed on the metal base, chip 910 ismounted on adhesive 964, connection joint 966 is formed and thenencapsulant 968 is formed.

Thereafter, metal pillar 970 is formed by applying a wet chemical etchin the same manner that metal pillar 170 is formed. The wet chemicaletch is highly selective of copper with respect to nickel, polyimide andthe molding compound, and therefore, highly selective of the metal basewith respect to the nickel layer of routing line 936, the nickel layerof the etch mask, adhesive 964 and encapsulant 968. Furthermore, thenickel layer of routing line 936 protects the copper layer of routingline 936 from the wet chemical etch. Therefore, no appreciable amount ofrouting line 936, adhesive 964 or encapsulant 968 is removed. Althoughthe wet chemical etch is highly selective of the copper layer of theetch mask and removes the copper layer of the etch mask, and the etchmask becomes much thinner, this is relatively unimportant since thenickel layer of the etch mask contacts the metal base and remainsintact.

Thereafter, the etch mask is removed. The etch mask, which at this stageconsists of a nickel layer, is removed by wet chemical etching using anickel etching solution, such as a dilute mixture of nitric andhydrochloric acid, that is highly selective of nickel with respect topolyimide and the molding compound. The wet chemical etch also removesthe exposed portion of the nickel layer of routing line 936 (thatextends laterally beyond metal pillar 970 and downwardly beyond thecopper layer of routing line 936), and the elongated routing portion ofrouting line 936 becomes slightly thinner. However, no appreciableamount of adhesive 964 or encapsulant 968 is removed.

Since the etch mask is extremely thin relative to metal pillar 970, andthe structure is removed from the nickel etching solution soon after theetch mask is stripped, it is not critical that the nickel etchingsolution be highly selective of nickel with respect to copper. In fact,the nickel etching solution is also selective of copper. As a result,the nickel etching solution also removes a slight amount of the exposedcopper surfaces. However, the nickel etching solution is not appliedlong enough to appreciably affect the copper features.

The nickel etching solution has no significant impact on routing line936 or metal pillar 970. The optimal etch time for exposing the etchmask to the wet chemical etch in order to remove the etch mask withoutsignificantly impacting routing line 936 or metal pillar 970 can beestablished through trial and error.

The nickel etching solution converts routing line 936 from a flat,planar lead to an essentially flat, planar lead due to the slight recess(not shown) previously occupied by a portion of the nickel layer thatextended laterally beyond metal pillar 970 and a lower portion of aportion of the copper layer that extended laterally beyond metal pillar970. In addition, the nickel etching solution exposes pillar tip 974.

Thereafter, insulative base 982 is formed with a thickness of 220microns (rather than 250 microns), and then the lower portion ofinsulative base 982 is removed by grinding. Initially, the diamond sandwheel grinds only insulative base 982. As the grinding continues,insulative base 982 becomes thinner as the grinded surface migratesupwardly. Eventually the diamond sand wheel contacts metal pillar 970,and as a result, begins to grind metal pillar 970 as well. As thegrinding continues, metal pillar 970 and insulative base 982 becomethinner as their grinded surfaces migrate upwardly. The grindingcontinues until metal pillar 970 and insulative base 982 have thedesired thickness, and then halts before it reaches chip 910, routingline 936, plated contact 946, adhesive 964, connection joint 966 orencapsulant 968. Thereafter, the structure is rinsed in distilled waterto remove contaminants.

The grinding removes a 10 micron thick lower portion of metal pillar 970and a 30 micron thick lower portion of insulative base 982. As a result,chip 910 remains embedded in encapsulant 968, metal pillar 970 remainsembedded in insulative base 982, routing line 936 remains unexposed andmetal pillar 970 is exposed. Furthermore, metal pillar 970 andinsulative base 982 are laterally aligned with one another at a surfacethat faces downwardly. Thus, an exposed planarized horizontal surfacethat faces downwardly includes metal pillar 970 and insulative base 982.

Contact terminal 986 is then electrolessly plated on metal pillar 970.Contact terminal 986 is composed of a nickel layer electrolessly platedon metal pillar 970 and a gold layer electrolessly plated on the nickellayer. The nickel layer contacts and is sandwiched between metal pillar970 and the gold layer, and the gold layer is spaced from metal pillar970 and exposed. For convenience of illustration, the nickel and goldlayers are shown as a single layer.

The structure is dipped in an activator solution such as dilutepalladium chloride of approximately 0.1 grams of palladium chloride and5 cubic centimeters of hydrochloric acid per liter of water to rendermetal pillar 970 catalytic to electroless nickel, then the structure isrinsed in distilled water to remove the palladium from encapsulant 968and insulative base 982.

The structure is then submerged in an electroless nickel platingsolution such as Enthone Enplate NI-424 at 85° C.

Metal pillar 970 is catalytic to electroless nickel. Furthermore,encapsulant 968 and insulative base 982 are not catalytic to electrolessnickel and therefore a plating mask is not necessary. As a result,contact terminal 986 plates on metal pillar 970.

The electroless nickel plating operation continues until contactterminal 986 is 4 microns thick. At this point, contact terminal 986 isprimarily nickel and contain about 4 to 9 weight percentage phosphorus.

Thereafter, the structure is removed from the electroless nickel platingsolution and briefly submerged in an electroless gold plating solutionsuch as is MacDermid PLANAR™ at 70° C. Contact terminal 986 includes anexposed nickel surface layer and therefore is catalytic to electrolessgold. Furthermore, encapsulant 968 and insulative base 982 are notcatalytic to electroless gold and therefore a plating mask is notnecessary. As a result, the gold deposits on the nickel surface layer.The gold electroless plating operation continues until the gold surfacelayer is 0.5 microns thick. Thereafter, the structure is removed fromthe electroless gold plating solution and rinsed in distilled water.

Contact terminal 986 contacts and is electrically connected to metalpillar 970 and extends downwardly beyond metal pillar 970 and insulativebase 982. Thus, contact terminal 986 is spaced from and extendsdownwardly beyond chip 910, routing line 936, adhesive 964, connectionjoint 966 and encapsulant 968. Moreover, contact terminal 986 provides arobust, permanent electrical connection to metal pillar 970 thatprotrudes downwardly from metal pillar 970 and is exposed. Contactterminal 986 includes a buried nickel layer and a gold surface layer.The buried nickel layer provides the primary mechanical and electricalconnection to metal pillar 970, and the gold surface layer provides awettable surface to facilitate solder reflow. Contact terminal 986 has acircular shape with a diameter of 200 microns, includes a gold (ratherthan solder) surface 990A and lacks a flange (corresponding to flange192).

The conductive traces each include a contact terminal with an exposedgold surface to provide a land grid array (LGA) package.

Semiconductor chip assembly 998 includes chip 910, routing line 936,plated contact 946, adhesive 964, connection joint 966, encapsulant 968,metal pillar 970, insulative base 982 and contact terminal 986.

FIGS. 34A, 34B and 34C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with atenth embodiment of the present invention. In the tenth embodiment, thepillar etch mask has its wing removed. For purposes of brevity, anydescription in the first embodiment is incorporated herein insofar asthe same is applicable, and the same description need not be repeated.Likewise, elements of the tenth embodiment similar to those in the firstembodiment have corresponding reference numerals indexed at one-thousandrather than one-hundred. For instance, chip 1010 corresponds to chip110, routing line 1036 corresponds to routing line 136, etc.

Routing line 1036 and etch mask 1056 are formed in the same manner asrouting line 936 and the corresponding etch mask, respectively. Thus,routing line 1036 and etch mask 1056 are simultaneously formed on themetal base (corresponding to metal base 120) during an electroplatingoperation, and the solder layer (corresponding to solder layer 154) isomitted.

Thereafter, adhesive 1064 is formed on the metal base, chip 1010 ismounted on adhesive 1064, connection joint 1066 is formed and thenencapsulant 1068 is formed.

Thereafter, metal pillar 1070 is formed by applying a wet chemical etchin the same manner that metal pillar 970 is formed. As a result, the wetchemical etch removes the copper layer of etch mask 1056, and etch mask1056 becomes much thinner.

Thereafter, etch mask 1056, which at this stage consists of a nickellayer, has its wing removed. The wing is the portion of etch mask 1056that protrudes laterally from and does not contact metal pillar 1070.Thus, the wing is the portion of etch mask 1056 that is undercut by thewet chemical etch that forms metal pillar 1070. The wing includes asurface portion that corresponds to outer surface portion 192F, theremainder of etch mask 1056 includes a surface portion that correspondsto inner surface portion 192E, and the wing is separated from theremainder of etch mask 1056 at a boundary that corresponds to circularboundary 192G.

The wing is removed by rinsing the structure in distilled water during acleaning step that follows the wet chemical etch. Since etch mask 1056at this stage is extremely thin (1 micron), and the wing is notsupported by metal pillar 1070, the boundary between the wing and theremainder of etch mask 1056 is relatively fragile. As a result, thewater pressure from the distilled water rinse fractures etch mask 1056at the boundary with the wing, thereby dislodging the wing from theremainder of etch mask 1056. However, the remainder of etch mask 1056remains intact and continues to contact and cover pillar tip 1074 andtip sidewall portion 1076B.

Thereafter, insulative base 1082 is formed and grinded in the samemanner as insulative base 982. As a result, chip 1010 remains embeddedin encapsulant 1068, etch mask 1056 and metal pillar 1070 remainembedded in insulative base 1082, routing line 1036 remains unexposedand etch mask 1056 and metal pillar 1070 are exposed. In addition, etchmask 1056 is removed from pillar tip 1074 but continues to contact andcover tip sidewall portion 1076B. Furthermore, etch mask 1056, metalpillar 1070 and insulative base 1082 are laterally aligned with oneanother at a surface that faces downwardly. Thus, an exposed planarizedhorizontal surface that faces downwardly includes etch mask 1056, metalpillar 1070 and insulative base 1082.

Contact terminal 1086 is then electrolessly plated on etch mask 1056 andmetal pillar 1070 in the same manner that contact terminal 986 iselectrolessly plated on metal pillar 970.

The conductive traces each include a contact terminal with an exposedgold surface to provide a land grid array (LGA) package.

Semiconductor chip assembly 1098 includes chip 1010, routing line 1036,plated contact 1046, etch mask 1056, adhesive 1064, connection joint1066, encapsulant 1068, metal pillar 1070, insulative base 1082 andcontact terminal 1086.

FIGS. 35A, 35B and 35C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with aneleventh embodiment of the present invention. In the eleventhembodiment, the pillar etch mask is epoxy. For purposes of brevity, anydescription in the first embodiment is incorporated herein insofar asthe same is applicable, and the same description need not be repeated.Likewise, elements of the eleventh embodiment similar to those in thefirst embodiment have corresponding reference numerals indexed ateleven-hundred rather than one- hundred. For instance, chip 1110corresponds to chip 110, routing line 1136 corresponds to routing line136, etc.

The metal layer (corresponding to metal layer 152) and the solder layer(corresponding to solder layer 154) are omitted.

Etch mask 1156 is formed by depositing epoxy paste on the metal base(corresponding to metal base 120) and then curing. The epoxy paste issimilar to that used for insulative base 182. The epoxy paste isdeposited on the metal base using stencil printing. During the stencilprinting process, a stencil (not shown) with a thickness of 100 micronsis placed over the metal base, a stencil opening with a diameter of 450microns is vertically aligned with the trench (corresponding to trench130), and then a squeegee (not shown) pushes the epoxy paste along thesurface of the stencil opposite the metal base, through the stencilopening, onto the metal base and into the trench. The epoxy paste iscompliant enough at room temperature to conform to virtually any shape.As a result, the epoxy paste fills the trench and extends above themetal base in the stencil opening. Thereafter, the stencil is removedand the epoxy paste is cured or hardened at a relatively low temperaturein the range of 100 to 250° C. to form a solid adherent insulator thatprovides etch mask 1156 with dimensions similar to etch mask 156.

Thereafter, adhesive 1164 is formed on the metal base, chip 1110 ismounted on adhesive 1164, connection joint 1166 is formed, encapsulant1168 is formed and then metal pillar 1170 is formed.

Thereafter, insulative base 1182 is formed and grinded in the samemanner as insulative base 982. As a result, chip 1110 remains embeddedin encapsulant 1168, etch mask 1156 and metal pillar 1170 remainembedded in insulative base 1182, routing line 1136 remains unexposedand etch mask 1156 and metal pillar 1170 are exposed. In addition, etchmask 1156 is removed from pillar tip 1174 but continues to contact andcover tip sidewall portion 11 76B. Furthermore, etch mask 1156, metalpillar 1170 and insulative base 1182 are laterally aligned with oneanother at a surface that faces downwardly. Thus, an exposed planarizedhorizontal surface that faces downwardly includes etch mask 1156, metalpillar 1170 and insulative base 1182.

Contact terminal 1186 is then electrolessly plated on metal pillar 1170in the same manner that contact terminal 986 is electrolessly plated onmetal pillar 970.

The conductive traces each include a contact terminal with an exposedgold surface to provide a land grid array (LGA) package.

Semiconductor chip assembly 1198 includes chip 1110, routing line 1136,plated contact 1146, etch mask 1156, adhesive 1164, connection joint1166, encapsulant 1168, metal pillar 1170, insulative base 1182 andcontact terminal 1186.

FIGS. 36A, 36B and 36C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with atwelfth embodiment of the present invention. In the twelfth embodiment,the plated contact and the metal layer are simultaneously formed. Forpurposes of brevity, any description in the first embodiment isincorporated herein insofar as the same is applicable, and the samedescription need not be repeated. Likewise, elements of the twelfthembodiment similar to those in the first embodiment have correspondingreference numerals indexed at twelve-hundred rather than one-hundred.For instance, chip 1210 corresponds to chip 110, routing line 1236corresponds to routing line 136, etc.

Plated contact 1246 and metal layer 1252 are simultaneously formedduring an electroplating operation. This is accomplished by a slightadjustment to the electroplating operation previously described forplated contact 146. In particular, the photoresist layer (correspondingto photoresist layer 144) is patterned like the photoresist layer(corresponding to photoresist layer 150) for metal layer 152. As aresult, plated contact 1246 and metal layer 1252 are each composed of anickel layer electroplated on a copper surface and a gold layerelectroplated on the nickel layer. In plated contact 1246, the nickellayer is electroplated on the copper layer of routing line 1236,contacts and is sandwiched between routing line 1236 and the gold layer,is buried beneath the gold layer and has a thickness of 3 microns, andthe gold layer contacts the nickel layer, is spaced from routing line1236, is exposed and has a thickness of 0.5 microns. In metal layer1252, the nickel layer is electroplated on the metal base (correspondingto metal base 120), contacts and is sandwiched between the metal baseand the gold layer, is buried beneath the gold layer and has a thicknessof 3 microns, and the gold layer contacts the nickel layer, is spacedfrom the metal base, is exposed and has a thickness of 0.5 microns. Inaddition, the photoresist layers (corresponding to photoresist layers148 and 150) and related electroplating operation are omitted.

Thereafter, the solder layer (corresponding to solder layer 154) isformed. In metal layer 1252, the buried nickel layer provides theprimary mechanical and electrical connection for the solder layer to themetal base, and the gold surface layer provides a wettable surface tofacilitate solder reflow. Furthermore, the solder reflow is essentiallyconfined to metal layer 1252.

Semiconductor chip assembly 1298 includes chip 1210, routing line 1236,plated contact 1246, adhesive 1264, connection joint 1266, encapsulant1268, metal pillar 1270, insulative base 1282 and contact terminal 1286.

FIGS. 37A, 37B and 37C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with athirteenth embodiment of the present invention. In the thirteenthembodiment, the metal pillar is disposed within the periphery of thechip. For purposes of brevity, any description in the first embodimentis incorporated herein insofar as the same is applicable, and the samedescription need not be repeated. Likewise, elements of the thirteenthembodiment similar to those in the first embodiment have correspondingreference numerals indexed at thirteen-hundred rather than one-hundred.For instance, chip 1310 corresponds to chip 110, routing line 1336corresponds to routing line 136, etc.

Routing line 1336 extends within and outside the periphery of chip 1310,and metal pillar 1370 and contact terminal 1386 are disposed within theperiphery of chip 1310. This is accomplished by a slight adjustment tothe etching operation previously described for trench 130 and theelectroplating operation previously described for routing line 136 andetch mask 156. In particular, the photoresist layer (corresponding tophotoresist layer 128) is pattemed to laterally shift the opening forthe trench (corresponding to trench 130), and therefore the trench islaterally shifted relative to trench 130. Thereafter, the photoresistlayer (corresponding to photoresist layer 132) is patterned to reshapethe opening for routing line 1336 and the photoresist layer(corresponding to photoresist layer 150) is patterned to laterally shiftthe opening for the etch mask (corresponding to etch mask 156), andtherefore routing line 1336 is laterally shifted and rotated relative torouting line 136 and the etch mask is laterally shifted relative to etchmask 156. As a result, metal pillar 1370 and contact terminal 1386 aredisposed within the periphery of chip 1310.

Semiconductor chip assembly 1398 includes chip 1310, routing line 1336,plated contact 1346, adhesive 1364, connection joint 1366, encapsulant1368, metal pillar 1370, insulative base 1382 and contact terminal 1386.

FIGS. 38A, 38B and 38C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with afourteenth embodiment of the present invention. In the fourteenthembodiment, the metal pillar is inverted. For purposes of brevity, anydescription in the first embodiment is incorporated herein insofar asthe same is applicable, and the same description need not be repeated.

Likewise, elements of the fourteenth embodiment similar to those in thefirst embodiment have corresponding reference numerals indexed atfourteen-hundred rather than one-hundred. For instance, chip 1410corresponds to chip 140, routing line 1436 corresponds to routing line136, etc.

The metal base (corresponding to metal base 120) has a thickness of 500microns (rather than 150 microns). Thereafter, routing line 1436 isformed on the downwardly facing surface (corresponding to surface 124)of the metal base, and the trench (corresponding to trench 130) and theetch mask (corresponding to etch mask 156) are formed on the upwardlyfacing surface (corresponding to surface 122) of the metal base.

Thereafter, insulative base 1482 is deposited on routing line 1436 andthe metal base, and then insulative base 1482 is partially polymerizedand forms a gel.

Thereafter, the structure is placed on a support (not shown) similar tometal base 120 such that insulative base 1482 contacts the support andis sandwiched between the metal base and the support and between routingline 1436 and the support while insulative base 1482 is a gel, and theninsulative base 1482 is hardened.

Thereafter, metal pillar 1470 is formed, and then plated contact 1446 isformed.

Thereafter, adhesive 1464 is deposited on insulative base 1482, thenchip 1410 is placed on adhesive 1464, and then adhesive 1464 ishardened. Metal pillar 1470 is not disposed downwardly beyond chip 1410,and instead extends upwardly and downwardly beyond and vertically acrossthe thickness of chip 1410.

Thereafter, connection joint 1466 is formed, and then encapsulant 1468is formed. Encapsulant 1468 is similar to insulative base 182 (ratherthan encapsulant 168) and has a thickness of 700 microns (rather than400 microns). Accordingly, encapsulant 1468 is deposited on chip 1410,routing line 1436, adhesive 1464, connection joint 1466, metal pillar1470 and insulative base 1482, and then encapsulant 1468 is hardened.

Thereafter, encapsulant 1468 is grinded to expose the etch mask, andthen contact terminal 1486 is formed.

Semiconductor chip assembly 1498 includes chip 1410, routing line 1436,plated contact 1446, adhesive 1464, connection joint 1466, encapsulant1468, metal pillar 1470, insulative base 1482 and contact terminal 1486.

FIGS. 39A, 39B and 39C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with afifteenth embodiment of the present invention. In the fifteenthembodiment, the assembly is a multi-chip package. For purposes ofbrevity, any description in the first embodiment is incorporated hereininsofar as the same is applicable, and the same description need not berepeated. Likewise, elements of the fifteenth embodiment similar tothose in the first embodiment have corresponding reference numeralsindexed at fifteen-hundred rather than one-hundred. For instance, chip1510 corresponds to chip 110, routing line 1536 corresponds to routingline 136, etc.

Plated contact 1546 is lengthened. This is accomplished by a slightadjustment to the electroplating operation previously described forplated contact 146. In particular, the photoresist layer (correspondingto photoresist layer 142) is patterned to lengthen the opening forplated contact 1546, and therefore plated contact 1546 is lengthenedrelative to plated contact 146.

Chip 1510 is mechanically attached to routing line 1536 by adhesive 1564and electrically connected to routing line 1536 by connection joint1566.

Thereafter, adhesive 1565 is deposited as a spacer paste that includessilicon spacers on chip 1510, then chip 1511 (which includes pad 1517and is essentially identical to chip 1510) is placed on adhesive 1565such that adhesive 1565 contacts and is sandwiched between chips 1510and 1511, and then the structure is placed in an oven and adhesive 1565is fully cured (C stage) at relatively low temperature in the range of150 to 200° CC. to form a solid adhesive insulative layer thatmechanically attaches chips 1510 and 1511. Adhesive 1565 is 100 micronsthick between chips 1510 and 1511, and chips 1510 and 1511 are spacedand separated from and vertically aligned with one another. A suitablespacer paste is Hysol QMI 500.

Thereafter, chip 1511 is electrically connected to routing line 1536 byconnection joint 1567 in the same manner that chip 1510 is electricallyconnected to routing line 1536 by connection joint 1566.

Thereafter, encapsulant 1568 with a thickness of 700 microns (ratherthan 400 microns) is formed so that encapsulant 1568 contacts and coverschips 1510 and 1511, routing line 1536, plated contact 1546, adhesives1564 and 1565 and connection joints 1566 and 1567, and then metal pillar1570, insulative base 1582 and contact terminal 1586 are formed.

The semiconductor chip assembly is a multi-chip first-level package.Chips 1510 and 1511 are embedded in encapsulant 1568. Furthermore, anelectrically conductive path between pad 1516 and metal pillar 1570 notonly includes but also requires routing line 1536, and an electricallyconductive path between pad 1517 and metal pillar 1570 not only includesbut also requires routing line 1536. Thus, chips 1510 and 1511 are bothembedded in encapsulant 1568 and electrically connected to metal pillar1570 by an electrically conductive path that includes routing line 1536.

Semiconductor chip assembly 1598 includes chips 1510 and 1511, routingline 1536, plated contact 1546, adhesives 1564 and 1565, connectionjoints 1566 and 1567, encapsulant 1568, metal pillar 1570, insulativebase 1582 and contact terminal 1586.

FIGS. 40, 41, 42, 43 and 44 are cross-sectional views of metal pillars1670, 1770, 1870, 1970 and 2070, respectively, in accordance with asixteenth to twentieth embodiment of the present invention.

Metal pillars 1670, 1770, 1870, 1970 and 2070 have increasingly narrowshape as the wet chemical etch that forms the metal pillar increasinglyundercuts the flange, for instance by increasing the etch concentrationor the etch time. Metal pillars 1670, 1770, 1870, 1970 and 2070 alsohave generally conical shapes with a diameter that substantiallycontinuously decreases from the pillar base to the pillar tip as themetal pillar extends downwardly. Moreover, metal pillars 1670, 1770,1870, 1970 and 2070 have identical pillar tips. That is, the pillar tipsare unaffected by the wet chemical etch, and therefore the pillar tipsare precisely-controlled despite variations in the wet chemical etch.

In metal pillars 1670 and 1770 the spike is located between the flangetip and the outer diameter of the flange, in metal pillar 1870 the spikeis located at the flange is tip, and in metal pillars 1970 and 2070 thespike is located between the flange tip and the inner diameter of theflange. Thus, the wet chemical etch that forms metal pillars 1670 and1770 undercuts the outer diameter of the flange without undercutting theflange tip or the inner diameter of the flange, the wet chemical etchthat forms metal pillar 1870 undercuts the outer diameter of the flangeare reaches the flange tip without undercutting the inner diameter ofthe flange, and the wet chemical etch that forms metal pillars 1970 and2070 undercuts the flange tip and the outer diameter of the flangewithout undercutting the inner diameter of the flange.

In metal pillars 1670, 1770, 1870, 1970 and 2070 the pillar base and thepillar tip face in opposite directions, the tapered sidewalls includebase and tip sidewall portions that are adjacent to one another at thespike, the base sidewall portion is a concave arc that is adjacent tothe pillar base, is spaced from the pillar tip, slants inwardly towardsthe pillar tip and extends upwardly beyond the tip sidewall portion, thetip sidewall portion is a concave arc that is adjacent to the pillartip, is spaced from the pillar base, slants inwardly towards the pillartip and extends downwardly beyond the base sidewall portion, and thespike protrudes laterally from the metal pillar, is spaced from thepillar base and the pillar tip, spans 360 degrees laterally around themetal pillar at a constant vertical distance from the pillar base andthe pillar tip and provides an abrupt discontinuity between the base andtip sidewall portions. In addition, the pillar base and the pillar tipare flat and parallel to one another, the pillar tip is disposed withina surface area of the pillar base, and a surface area of the pillar baseis at least 20 percent larger than a surface area of the pillar tip.

In metal pillars 1670, 1770, 1870, 1970 and 2070 the base sidewallportion extends vertically only upwardly beyond the spike. In metalpillars 1670, 1770, 1870 and 1970 the base sidewall portion has amaximum diameter at the pillar base and a minimum diameter at the spikeand extends laterally only outwardly beyond the spike, whereas in metalpillar 2070 the base sidewall portion has a maximum diameter at thepillar base and a minimum diameter near but spaced from the spike andextends laterally inwardly and outwardly beyond the spike.

In metal pillars 1670, 1770, 1870, 1970 and 2070 the tip sidewallportion has a maximum diameter at the spike and a minimum diameter atthe pillar tip and extends laterally only inwardly beyond the spike. Inmetal pillars 1870, 1970 and 2070 the tip sidewall portion extendsvertically only downwardly beyond the spike, whereas in metal pillars1670 and 1770 the tip sidewall portion extends vertically upwardly anddownwardly beyond the spike.

The semiconductor chip assemblies described above are merely exemplary.Numerous other embodiments are contemplated. For instance, the platedcontact and the insulative base can be omitted. In addition, theembodiments described above can generally be combined with one another.For instance, the flip-chip in the second embodiment and the platedconnection joints in the third and fourth embodiments can be used in theother embodiments except for the multi-chip assembly in the twelfthembodiment since the chips are not inverted. Likewise, the contactterminals in the fifth and sixth embodiments can be used in the otherembodiments except for the ninth, tenth and eleventh embodiments sinceother contact terminals are formed. Likewise, the omitted insulativebase in the eighth embodiment can be used in the other embodiments.Likewise, the pillar etch masks removed from the pillar tips in theninth, tenth and eleventh embodiments can be used in the otherembodiments except for the fifth and sixth embodiments since the pillaretch masks provide the contact terminals. Likewise, the pillar etch maskin the twelfth embodiment and the metal pillars in the thirteenth andfourteenth embodiments can be used in the other embodiments.

Likewise, the multi-chip assembly in the fifteenth embodiment can beused in the other embodiments except for the second to fourthembodiments since the chips are inverted. Likewise, the metal pillars inthe sixteen, seventeen, eighteenth, nineteenth and twentieth embodimentscan be used in the first to fifteenth embodiments. The embodimentsdescribed above can be mixed-and-matched with one another and with otherembodiments depending on design and reliability considerations.

The metal base need not necessarily be removed within the periphery ofthe chip. For instance, a portion of the metal base that extends withinthe periphery of the chip and is spaced from the metal pillar can remainintact and provide a heat sink.

The pillar etch mask can be a wide variety of materials includingcopper, gold, nickel, palladium, tin, solder, photoresist, epoxy, andcombinations thereof, can be a conductor or an insulator, can be formedby a wide variety of processes including electroplating, electrolessplating, printing, reflowing, curing, and combinations thereof, and canhave a wide variety of shapes and sizes. For instance, the pillar etchmask can formed by a single process such as electroplating, solder pastedeposition and reflow or epoxy paste deposition and curing, oralternatively, multiple processes such as electroplating followed bysolder paste deposition and reflow. Advantageously, an electroplatedmetal layer can provide a wettable surface and the solder pastedeposition and reflow can form a solder layer more rapidly thanelectroplating the metal layer to the thickness of the solder layer,thereby improving manufacturing throughput.

Furthermore, the metal layer (or exposed surface thereof) can be variouswettable metals including gold, tin and solder, particularly if solderreflow occurs thereon, or alternatively, the metal layer (or exposedsurface thereof) can be various non-wettable metals, particularly ifsolder reflow does not occur thereon.

The pillar etch mask can be deposited on the metal base before, duringor after the routing line is deposited on the metal base, before orafter the chip is attached to the routing line, before or after theencapsulant is formed and before, during or after the connection jointis formed. For instance, an electroplated metal layer can besimultaneously formed with the routing line, the plated contact or theconnection joint, thereby improving manufacturing throughput. Inaddition, the solder layer can be formed on the metal layer before orafter the routing line is deposited on the metal base, before or afterthe chip is attached to the routing line, before or after theencapsulant is formed, before or after the connection joint is formed,before or after the metal pillar is formed and before or after theinsulative base is formed. Likewise, the solder layer can be formed onthe metal layer before or after the photoresist layer (corresponding tophotoresist layer 150) that defines the metal layer is removed. Forinstance, the photoresist layer that defines the metal layer can remainintact during the solder paste deposition and reflow to assist withconfining the solder layer to the metal layer.

The pillar etch mask can be a conductor that includes the metal layer.For instance, the pillar etch mask can be the metal layer and the solderlayer, particularly if the pillar etch mask is not removed from thepillar tip after the metal pillar is formed, or alternatively, thepillar etch mask can be the metal layer, particularly if the pillar etchmask is removed from the pillar tip after the metal pillar is formed.The pillar etch mask can also be an insulator that excludes the metallayer. For instance, the pillar etch mask can be epoxy, particularly ifthe pillar etch mask is removed from the pillar tip after the metalpillar is formed.

The pillar etch mask can remain permanently attached to the metal pillaror be removed after the metal pillar is formed.

The pillar etch mask can be reshaped to conformally coat the pillar tipand the tip sidewall portion but remain spaced from the base sidewallportion, for instance by dislodging the wing by mechanical brushing,sand blasting, air blowing or water rinsing, or by reflowing a pillaretch mask composed of solder when the metal pillar does not provide awettable surface. Alternatively, a pillar etch mask composed of soldercan be reflowed to conformally coat the metal pillar (including thepillar tip, the tip sidewall portion and the base sidewall portion), forinstance by depositing flux on the metal pillar so that the metal pillarprovides a wettable surface before the solder reflow operation.

The routing line can be various conductive metals including copper,gold, nickel, silver, palladium, tin, combinations thereof, and alloysthereof. The preferred composition of the routing line will depend onthe nature of the connection joint as well as design and reliabilityfactors. Furthermore, those skilled in the art will understand that inthe context of a semiconductor chip assembly, a copper material istypically a copper alloy that is mostly copper but not pure elementalcopper, such copper-zirconium (99.9% copper),copper-silver-phosphorus-magnesium (99.7% copper), orcopper-tin-iron-phosphorus (99.7% copper). Likewise, the routing linecan fan-in as well as fan-out.

The routing line can be formed on the metal base by numerous depositiontechniques including electroplating and electroless plating. Inaddition, the routing line can be deposited on the metal base as asingle layer or multiple layers. For instance, the routing line can be a10 micron layer of gold, or alternatively, a 9.5 micron layer of nickelelectroplated on a 0.5 micron layer of gold electroplated on a copperbase to reduce costs, or alternatively, a 9 micron layer of nickelelectroplated on a 0.5 micron layer of gold electroplated on a 0.5micron layer of tin electroplated on a copper base to reduce costs andavoid gold-copper alloys that may be difficult to remove when the copperbase is etched. As another example, the routing line can consist of anon-copper layer electroplated on a copper base and a copper layerelectroplated on the non-copper layer. Suitable non-copper layersinclude nickel, gold, palladium and silver. After the routing line isformed, a wet chemical etch can be applied that is highly selective ofcopper with respect to the non-copper layer to etch the copper base andexpose the routing line without removing the copper or non-copperlayers. The non- copper layer provides an etch stop that prevents thewet chemical etch from removing the copper layer. Furthermore, it isunderstood that in the context of the present invention, the routingline and the metal base are different metals (or metallic materials)even if a multi-layer routing line includes a single layer that issimilar to the metal base (such as the example described above) or asingle layer of a multi-layer metal base.

The routing line can also be formed by etching a metal layer attached tothe metal base. For instance, a photoresist layer can be formed on themetal layer, the metal layer can be etched using the photoresist layeras an etch mask, and then the photoresist layer can be stripped.Alternatively, a photoresist layer can be formed on the metal layer, aplated metal can be selectively electroplated on the metal layer usingthe photoresist layer as a plating mask, the photoresist layer can bestripped, and then the metal layer can be etched using the plated metalas an etch mask. In this manner, the routing line can be formedsemi-additively and include unetched portions of the metal layer and theplated metal. Likewise, the routing line can be formed subtractivelyfrom the metal layer, regardless of whether the plated metal etch maskremains attached to the routing line.

The routing line can be spot plated near the pad to make it compatiblewith receiving the connection joint. For instance, a copper routing linecan be spot plated with nickel and then silver to make it compatiblewith a gold ball bond connection joint and avoid the formation ofbrittle silver-copper intermetallic compounds. Likewise, the pillar etchmask can be spot plated to make it compatible with receiving a soldermaterial. For instance, a nickel pillar etch mask can be spot platedwith gold to facilitate solder reflow.

The metal pillar can have a wide variety of shapes and sizes. Forinstance, the pillar base and the pillar tip can have a circular,rectangular or square shape. For example, the trench can haverectangular inner and outer peripheries so that the pillar etch mask,the pillar base and the pillar tip have rectangular shapes. In addition,the pillar base can have a diameter that is less than, equal to orgreater than the diameter of the pillar tip and the outer periphery ofthe trench. For example, the pillar base and the enlarged circularportion of the routing line upon which the pillar base is mounted canhave diameters that are at least 100 microns less than the outerperiphery of the trench to facilitate high-density circuitry.

The metal pillar can be uncovered in the downward direction by theencapsulant, the insulative base or any other insulative material of theassembly. For instance, the metal pillar can be exposed in the downwarddirection, or alternatively, the metal pillar can be unexposed in thedownward direction and the contact terminal that contacts and isoverlapped by the metal pillar can be exposed in the downward direction,or alternatively, the metal pillar can be unexposed in the downwarddirection, a plated terminal that contacts and is overlapped by themetal pillar can be unexposed in the downward direction, and a solderterminal that contacts and is overlapped by the plated terminal and isspaced from and overlapped by the metal pillar can be exposed in thedownward direction, or altematively, the metal pillar can be covered inthe downward direction by an insulative material external to theassembly such as another semiconductor chip assembly in a stackedarrangement. In every case, the metal pillar is not covered in thedownward direction by the encapsulant, the insulative base or any otherinsulative material of the assembly. s Further details regarding a metalpillar that is etched from a metal base and contacts a routing line aredisclosed in U.S. application Ser. No. 10/714,794 filed Nov. 17, 2003 byChuen Rong Leu et al. entitled “Semiconductor Chip Assembly withEmbedded Metal Pillar,” U.S. application Ser. No. 10/994,604 filed Nov.22, 2004 by Charles W. C Lin et al. entitled “Semiconductor ChipAssembly with Bumped Metal Pillar” and U.S. application Ser. No.10/994,836 filed Nov. 22, 2004 by Charles W. C Lin et al. entitled“Semiconductor Chip Assembly with Carved Bumped Terminal” which areincorporated by reference.

The conductive trace can function as a signal, power or ground layerdepending on the purpose of the associated chip pad.

The pad can have numerous shapes including a flat rectangular shape anda bumped shape. If desired, the pad can be treated to accommodate theconnection joint.

Numerous adhesives can be applied to mechanically attach the chip to therouting line. For instance, the adhesive can be applied as a paste, alaminated layer, or a liquid applied by screen-printing, spin-on, orspray-on. The adhesive can be a single layer that is applied to themetal base or a solder mask and then contacted to the chip or a singlelayer that is applied to the chip and then contacted to the metal baseor a solder mask. Similarly, the adhesive can be multiple layers with afirst layer applied to the metal base or a solder mask, a second layerapplied to the chip and then the layers contacted to one another.Thermosetting adhesive liquids and pastes such as epoxies are generallysuitable. Likewise, thermoplastic adhesives such as an insulativethermoplastic polyimide film with a glass transition temperature (Tg) of400° C. are also generally suitable. Silicone adhesives are alsogenerally suitable.

The encapsulant can be deposited using a wide variety of techniquesincluding printing and transfer molding. For instance, the encapsulantcan be printed on the chip as an epoxy paste and then cured or hardenedto form a solid adherent protective layer. The encapsulant can be any ofthe adhesives mentioned above. Moreover, the encapsulant need notnecessarily contact the chip. For instance, a glob-top coating can bedeposited on the chip after attaching the chip to the routing line, andthen the encapsulant can be formed on the glob-top coating.

The insulative base may be rigid or flexible, and can be variousdielectric films or prepregs formed from numerous organic or inorganicinsulators such as tape (polyimide), epoxy, silicone, glass, aramid andceramic. Organic insulators are preferred for low cost, high dielectricapplications, whereas inorganic insulators are preferred when highthermal dissipation and a matched thermal coefficient of expansion areimportant. For instance, the insulative base can initially be an epoxypaste that includes an epoxy resin, a curing agent, an accelerator and afiller, that is subsequently cured or hardened to form a solid adherentinsulative layer. The filler can be an inert material such as silica(powdered fused quartz) that improves thermal conductivity, thermalshock resistance and thermal coefficient of expansion matching. Organicfiber reinforcement may also be used in resins such as epoxy, cyanateester, polyimide, PTFE and combinations thereof. Fibers that may be usedinclude aramid, polyester, polyamide, poly-ether-ether-ketone,polyimide, polyetherimide and polysulfone. The fiber reinforcement canbe woven fabric, woven glass, random microfiber glass, woven quartz,woven, aramid, non-woven fabric, non-woven aramid fiber or paper.Commercially available dielectric materials such as SPEEDBOARD C prepregby W. L. Gore & Associates of Eau Claire, Wis. are suitable.

The insulative base can be deposited in numerous manners, includingprinting and transfer molding. Furthermore, the insulative base can beformed before or after attaching the chip to the routing line.

The insulative base can have its lower portion removed using a widevariety of techniques including grinding (including mechanical polishingand chemical-mechanical polishing), blanket laser ablation and blanketplasma etching. Likewise, the insulative base can have a selectedportion below the metal pillar removed using a wide variety oftechniques including selective laser ablation, selective plasma etchingand photolithography.

The insulative base can be laterally aligned with the pillar etch maskalong a downwardly facing surface that extends downwardly beyond therouting line and the metal pillar by grinding the insulative basewithout grinding the pillar etch mask, the metal pillar or the routingline, then grinding the insulative base and the pillar etch mask withoutgrinding the metal pillar or the routing line, and then discontinuingthe grinding before reaching the metal pillar. Likewise, the insulativebase can be laterally aligned with the contact terminal along adownwardly facing surface that extends downwardly beyond the routingline and the metal pillar by grinding the insulative base withoutgrinding the contact terminal, the metal pillar or the routing line,then grinding the insulative base and the contact terminal withoutgrinding the metal pillar or the routing line, and then discontinuingthe grinding before reaching the metal pillar. Likewise, the insulativebase can be laterally aligned with the metal pillar along a downwardlyfacing surface that extends downwardly beyond the routing line bygrinding the insulative base without grinding the metal pillar or therouting line, then grinding the insulative base and the metal pillarwithout grinding the routing line, and then discontinuing the grindingbefore reaching the routing line.

The connection joint can be formed from a wide variety of materialsincluding copper, gold, nickel, palladium, tin, alloys thereof, andcombinations thereof, can be formed by a wide variety of processesincluding electroplating, electroless plating, ball bonding, wirebonding, stud bumping, solder reflowing, conductive adhesive curing, andwelding, and can have a wide variety of shapes and sizes. The shape andcomposition of the connection joint depends on the composition of therouting line as well as design and reliability considerations. Furtherdetails regarding an electroplated connection joint are disclosed inU.S. application Ser. No. 09/865,367 filed May 24, 2001 by Charles W. C.Lin entitled “Semiconductor Chip Assembly with SimultaneouslyElectroplated Contact Terminal and Connection Joint” which isincorporated by reference. Further details regarding an electrolesslyplated connection joint are disclosed in U.S. application Ser. No.09/864,555 filed May 24, 2001 by Charles W. C. Lin entitled“Semiconductor Chip Assembly with Simultaneously Electrolessly PlatedContact Terminal and Connection Joint” which is incorporated byreference. Further details regarding a ball bond connection joint aredisclosed in U.S. application Ser. No. 09/864,773 filed May 24, 2001 byCharles W. C. Lin entitled “Semiconductor Chip Assembly with Ball BondConnection Joint” which is incorporated by reference. Further detailsregarding a solder or conductive adhesive connection joint are disclosedin U.S. application Ser. No. 09/927,216 filed Aug. 10, 2001 by CharlesW. C. Lin entitled “Semiconductor Chip Assembly with Hardened ConnectionJoint” which is incorporated by reference. Further details regarding awelded connection joint are disclosed in U.S. application Ser. No.10/302,642 filed Nov. 23, 2002 by Cheng-Lien Chiang et al. entitled“Method of Connecting a Conductive Trace to a Semiconductor Chip UsingPlasma Undercut Etching” which is incorporated by reference.

After the connection joint is formed, if a plating bus exists then it isdisconnected from the conductive trace. The plating bus can bedisconnected by mechanical sawing, laser cutting, chemical etching, andcombinations thereof. If the plating bus is disposed about the peripheryof the assembly but is not integral to the assembly, then the platingbus can be disconnected when the assembly is singulated from otherassemblies. However, if the plating bus is integral to the assembly, orsingulation has already occurred, then a photolithography step can beadded to selectively cut related circuitry on the assembly that isdedicated to the plating bus since this circuitry would otherwise shortthe conductive traces together. Furthermore, the plating bus can bedisconnected by etching the metal base.

A soldering material or solder ball can be deposited on the conductivetrace by plating or printing or placement techniques if required for thenext level assembly. However, the next level assembly may not requirethat the semiconductor chip assembly contain solder. For instance, inland grid array (LGA) packages, the soldering material is normallyprovided by the panel rather than the contact terminals on thesemiconductor chip assembly.

Various cleaning steps, such as a brief oxygen plasma cleaning step, ora brief wet chemical cleaning step using a solution containing potassiumpermanganate, can be applied to the structure at various stages, such asimmediately before forming the connection joint to clean the conductivetrace and the pad.

It is understood that, in the context of the present invention, any chipembedded in the encapsulant is electrically connected to the metalpillar by an electrically conductive path that includes the routing linemeans that the routing line is in an electrically conductive pathbetween the metal pillar and any chip embedded in the encapsulant. Thisis true regardless of whether a single chip is embedded in theencapsulant (in which case the chip is electrically connected to themetal pillar by an electrically conductive path that includes therouting line) or multiple chips are embedded in the encapsulant (inwhich case each of the chips is electrically connected to the metalpillar by an electrically conductive path that includes the routingline). This is also true regardless of whether the electricallyconductive path includes or requires a connection joint and/or a platedcontact between the routing line and the chip. This is also trueregardless of whether the electrically conductive path includes orrequires a passive component such as a capacitor or a resistor. This isalso true regardless of whether multiple chips are electricallyconnected to the routing line by multiple connection joints, and themultiple connection joints are electrically connected to one anotheronly by the routing line. This is also true regardless of whethermultiple chips are electrically connected to the metal pillar bydifferent electrically conductive paths (such as the multiple connectionjoint example described above) as long as each of the electricallyconductive paths includes the routing line.

It is also understood that, in the context of the present invention, thewet chemical etch that forms the metal pillar need not begin to form themetal pillar. For instance, a first wet chemical etch can form thepillar tip and the tip sidewall portion, and a second wet chemical etchcan form the pillar base and the base sidewall portion.

In this instance, the second wet chemical etch completes formation ofthe metal pillar and thus forms the metal pillar.

It is also understood that, in the context of the present invention, themetal pillar can include tapered sidewalls that are adjacent to andextend between the pillar base and the pillar tip and slant inwardlyeven though the inward slant may not be constant.

For instance, the tapered sidewalls can slant inwardly even if a portionof the tapered sidewalls adjacent to the spike slants outwardly as longas the pillar base has a larger diameter than the pillar tip and thetapered sidewalls mostly slant inwardly as they extend from the pillarbase to the pillar tip. Likewise, the base sidewall portion can slantinwardly even though the inward slant may not be constant. For instance,the base sidewall portion can slant inwardly even if a portion of thebase sidewall portion adjacent to the spike slants outwardly as long asthe pillar base has a larger diameter than the spike and the basesidewall portion mostly slants inwardly as it extends from the pillarbase to the spike. Likewise, the tip sidewall portion can slant inwardlyeven though the inward slant may not be constant. For instance, the tipsidewall portion can slant inwardly even if a portion of the tipsidewall portion adjacent to the pillar etch mask slants outwardly aslong as the spike has a larger diameter than the pillar tip and the tipsidewall portion mostly slants inwardly as it extends from the spike tothe pillar tip.

It is also understood that, in the context of the present invention, thespike can protrude laterally from the metal pillar even if the spikealso protrudes in the upward or downward direction. For instance, thespike can protrude laterally from the metal pillar even if the spikeprotrudes 15, 30, 45, 60 or 75 degrees in the downward directionrelative to the lateral plane.

It is also understood that, in the context of the present invention, thecontact terminal can include the flange of the pillar etch mask eventhough the flange may be altered between forming the pillar etch maskand forming the contact terminal. For instance, the shape of the flangemay be slightly altered during intervening process steps such as the wetchemical etch that forms the metal pillar, the cure that forms theinsulative base, the grinding that exposes the pillar etch mask and thesolder reflow that forms the contact terminal. Likewise, the solderreflow that forms the contact terminal may reflow the flange and alterthe composition of the flange. In each instance, the flange maintainsessentially constant size, shape and location and therefore the contactterminal includes the flange. Similarly, the contact terminal includesthe flange if the contact terminal is provided by the pillar etch mask.

The “upward” and “downward” vertical directions do not depend on theorientation of the assembly, as will be readily apparent to thoseskilled in the art. For instance, the encapsulant extends verticallybeyond the routing line in the “upward” direction, the metal pillarextends vertically beyond the chip in the “downward” direction and theinsulative base extends vertically beyond the encapsulant in the“downward” direction, regardless of whether the assembly is invertedand/or mounted on a printed circuit board. Likewise, the routing lineextends “laterally” beyond the metal pillar regardless of whether theassembly is inverted, rotated or slated. Thus, the “upward” and“downward” directions are opposite one another and orthogonal to the“lateral” direction, and the “laterally aligned” surfaces are coplanarwith one another in a lateral plane orthogonal to the upward anddownward directions. Moreover, the chip is shown above the routing line,the metal pillar and the insulative base, and the encapsulant is shownabove the chip, the routing line, the metal pillar and the insulativebase with a single orientation throughout the drawings for ease ofcomparison between the figures, although the assembly and its componentsmay be inverted at various manufacturing stages.

The working format for the semiconductor chip assembly can be a singleassembly or multiple assemblies based on the manufacturing design. Forinstance, a single assembly that includes a single chip can bemanufactured individually.

Alternatively, numerous assemblies can be simultaneously batchmanufactured on a single metal base with a single encapsulant and asingle insulative base then separated from one another. For example, thetrenches for multiple assemblies can be simultaneously etched in themetal base, then the metal layers for multiple assemblies can besimultaneously electroplated on the metal base and into the trenches,then the routing lines for multiple assemblies can be simultaneouslyelectroplated on the metal base, then the plated contacts can besimultaneously electroplated on the corresponding routing lines, thenseparate spaced solder pastes for the respective etch masks can beselectively disposed on the corresponding metal layers, then the solderpastes can be simultaneously reflowed to form the solder layers and thepillar etch masks, then separate spaced adhesives for the respectiveassemblies can be selectively disposed on the metal base, then the chipscan be disposed on the corresponding adhesives, then the adhesives canbe simultaneously fully cured, then the connection joints can be formedon the corresponding plated contacts and pads, then the encapsulant canbe formed, then the metal base can be etched to simultaneously form themetal pillars, then the insulative base can be formed, then theinsulative base and the pillar etch masks can be simultaneously grinded,then separate spaced solder balls for the respective pillar etch maskscan be selectively disposed on the corresponding solder layers, then thesolder layers and solder balls can be simultaneously reflowed to formthe contact terminals, and then the encapsulant and the insulative basecan be cut, thereby separating the individual single chip-substrateassemblies.

The semiconductor chip assembly can have a wide variety of packagingformats as required by the next level assembly. For instance, theconductive traces can be configured so that the assembly is a grid arraysuch as a ball grid array (BGA), column grid array (CGA), land gridarray (LGA) or pin grid array (PGA).

The semiconductor chip assembly can be a first-level package that is asingle-chip package (such as the first to fourteenth embodiments) or amulti-chip package (such as the fifteenth embodiment). Furthermore, amulti-chip first-level package can include chips that are stacked andvertically aligned with one another or are coplanar and laterallyaligned with one another.

Advantageously, the semiconductor chip assembly of the present inventionis reliable and inexpensive. The encapsulant and the insulative base canprotect the chip from handling damage, provide a known dielectricbarrier for the conductive trace and protect the assembly fromcontaminants and unwanted solder reflow during the next level assembly.The encapsulant can provide mechanical support for the conductive traceas the metal base is etched to form the metal pillar. In addition, themetal pillar can have a precision-formed pillar tip, thereby improvingaccuracy and microelectronic packaging density. What's more, the contactterminal can be interlocked to the metal pillar, thereby improvingreliability. The mode of the connection can shift from the initialmechanical coupling to metallurgical coupling to assure sufficientmetallurgical bond strength. Furthermore, the conductive trace can bemechanically and metallurgically coupled to the chip without wirebonding, TAB, solder or conductive adhesive, although the process isflexible enough to accommodate these techniques if desired. The processis highly versatile and permits a wide variety of mature connectionjoint technologies to be used in a unique and improved manner.Furthermore, the metal pillar is particularly well-suited for reducingthermal mismatch related stress in the next level assembly and yieldsenhanced reliability for the next level assembly that exceeds that ofconventional BGA packages. As a result, the assembly of the presentinvention significantly enhances throughput, yield and performancecharacteristics compared to conventional packaging techniques. Moreover,the assembly of the present invention is well-suited for use withmaterials compatible with copper chip requirements.

Various changes and modifications to the presently preferred embodimentsdescribed herein will be apparent to those skilled in the art. Forinstance, the materials, dimensions and shapes described above aremerely exemplary. Such changes and modifications may be made withoutdeparting from the spirit and scope of the present invention as definedin the appended claims.

1. A semiconductor chip assembly, comprising: a semiconductor chip that includes first and second opposing surfaces, wherein the first surface of the chip includes a conductive pad; a conductive trace that includes a routing line and a metal pillar, wherein the metal pillar is a single-piece metal and includes first and second opposing surfaces and tapered sidewalls therebetween, the first surface of the metal pillar faces in a first direction and contacts and is non-integral with the routing line, the second surface of the metal pillar faces in a second direction opposite the first direction and is spaced from the routing line, the tapered sidewalls include first and second sidewall portions that are adjacent to one another at a spike in the metal pillar, the first sidewall portion is a concave arc that is adjacent to the first surface of the metal pillar, is spaced from the second surface of the metal pillar, slants inwardly towards the second surface of the metal pillar and extends vertically beyond the second sidewall portion in the first direction, the second sidewall portion is a concave arc that is adjacent to the second surface of the metal pillar, is spaced from the first surface of the metal pillar, slants inwardly towards the second surface of the metal pillar and extends vertically beyond the first sidewall portion in the second direction, and the spike protrudes laterally from the metal pillar and is spaced from the first and second surfaces of the metal pillar; a connection joint that electrically connects the routing line and the pad; and an encapsulant, wherein the chip is embedded in the encapsulant, the routing line extends laterally beyond the metal pillar, and the metal pillar extends vertically beyond the routing line in the second direction, does not cover the routing line in the second direction and is not covered in the second direction by the encapsulant or any other insulative material of the assembly.
 2. The assembly of claim 1, wherein the routing line is essentially flat and parallel to the first and second surfaces of the chip.
 3. The assembly of claim 1, wherein the metal pillar has a generally conical shape with a diameter that substantially continuously decreases from the first surface of the metal pillar to the second surface of the metal pillar.
 4. The assembly of claim 1, wherein the metal pillar excludes solder.
 5. The assembly of claim 1, wherein the metal pillar is copper.
 6. The assembly of claim 1, wherein the metal pillar is disposed vertically beyond the chip, the routing line, the connection joint and the encapsulant in the second direction.
 7. The assembly of claim 1, wherein the second surface of the metal pillar is flat and parallel to the first and second surfaces of the chip.
 8. The assembly of claim 1, wherein the second surface of the metal pillar is disposed within a surface area of the first surface of the metal pillar.
 9. The assembly of claim 1, wherein a surface area of the first surface of the metal pillar is at least 20 percent larger than a surface area of the second surface of the metal pillar.
 10. The assembly of claim 1, wherein the first sidewall portion has a maximum diameter at the first surface of the metal pillar and a minimum diameter at the spike, and the second sidewall portion has a maximum diameter at the spike and a minimum diameter at the second surface of the metal pillar.
 11. The assembly of claim 1, wherein the first sidewall portion extends vertically beyond the spike only in the first direction, and the second sidewall portion extends vertically beyond the spike only in the second direction.
 12. The assembly of claim 1, wherein the spike provides an abrupt discontinuity between the first and second sidewall portions.
 13. The assembly of claim 1, wherein the spike spans 360 degrees laterally around the metal pillar.
 14. The assembly of claim 1, wherein the spike is a first distance in the first direction from the first surface of the metal pillar and a second distance in the second direction from the second surface of the metal pillar, and the first distance is greater than the second distance.
 15. The assembly of claim 14, wherein the first distance is at most four times the second distance.
 16. The assembly of claim 14, wherein the first distance is about two times the second distance.
 17. The assembly of claim 14, wherein the first and second distances are constant as the spike spans 360 degrees laterally around the metal pillar.
 18. The assembly of claim 1, including an insulative base that contacts the routing line and the metal pillar, is overlapped by the chip, extends vertically beyond the chip, the routing line, the connection joint and the encapsulant in the second direction and extends vertically at least as far as the metal pillar in the second direction.
 19. The assembly of claim 18, including an insulative adhesive that contacts the chip and the encapsulant and extends vertically beyond the chip in the second direction.
 20. The assembly of claim 1, wherein the assembly is a first-level package.
 21. A semiconductor chip assembly, comprising: a semiconductor chip that includes first and second opposing surfaces, wherein the first surface of the chip includes a conductive pad; a conductive trace that includes a routing line and a metal pillar, wherein the metal pillar is a single-piece metal and includes first and second opposing surfaces and tapered sidewalls therebetween, the first surface of the metal pillar faces in a first direction and contacts and is non-integral with the routing line, the second surface of the metal pillar faces in a second direction opposite the first direction and is spaced from the routing line, the tapered sidewalls include first and second sidewall portions that are adjacent to one another at a spike in the metal pillar, the first sidewall portion is a continuous concave arc that is adjacent to the first surface of the metal pillar, is spaced from the second surface of the metal pillar, slants inwardly towards the second surface of the metal pillar and extends vertically beyond the second sidewall portion in the first direction, the second sidewall portion is a continuous concave arc that is adjacent to the second surface of the metal pillar, is spaced from the first surface of the metal pillar, slants inwardly towards the second surface of the metal pillar and extends vertically beyond the first sidewall portion in the second direction, the spike protrudes laterally from and spans 360 degrees laterally around the metal pillar, is spaced from the first and second surfaces of the metal pillar, and is a first distance in the first direction from the first surface of the metal pillar and a second distance in the second direction from the second surface of the metal pillar, and the first distance is greater than the second distance; a connection joint that electrically connects the routing line and the pad; an encapsulant; and an insulative base, wherein the chip is embedded in the encapsulant and extends vertically beyond the routing line, the metal pillar and the insulative base in the first direction, the routing line extends laterally beyond the metal pillar towards the chip, extends vertically beyond the metal pillar in the first direction and extends vertically beyond the chip in the second direction, the metal pillar is embedded in the insulative base, is disposed outside a periphery of the chip, extends vertically beyond the chip, the routing line, the connection joint and the encapsulant in the second direction, does not cover the routing line in the second direction and is not covered in the second direction by the encapsulant, the insulative base or any other insulative material of the assembly, the encapsulant contacts the chip and extends vertically beyond the chip, the routing line, the metal pillar, the connection joint and the insulative base in the first direction, and the insulative base contacts the routing line and the metal pillar, is overlapped by the chip and extends vertically beyond the chip, the routing line, the spike, the connection joint and the encapsulant in the second direction.
 22. The assembly of claim 21, wherein the chip extends vertically beyond the conductive trace in the first direction.
 23. The assembly of claim 21, wherein the routing line is essentially flat and parallel to the first and second surfaces of the chip.
 24. The assembly of claim 21, wherein the metal pillar has a generally conical shape with a diameter that substantially continuously decreases from the first surface of the metal pillar to the second surface of the metal pillar.
 25. The assembly of claim 21, wherein the metal pillar is copper.
 26. The assembly of claim 21, wherein the second surface of the metal pillar is flat and parallel to the first and second surfaces of the chip, a surface area of the second surface of the metal pillar is disposed within a surface area of the first surface of the metal pillar, and the surface area of the first surface of the metal pillar is at least 20 percent larger than the surface area of the second surface of the metal pillar.
 27. The assembly of claim 21, wherein the first sidewall portion has a maximum diameter at the first surface of the metal pillar and a minimum diameter at the spike, and the second sidewall portion has a maximum diameter at the spike and a minimum diameter at the second surface of the metal pillar.
 28. The assembly of claim 21, wherein the first sidewall portion extends vertically beyond the spike only in the first direction, and the second sidewall portion extends vertically beyond the spike only in the second direction.
 29. The assembly of claim 21, wherein the first sidewall portion extends vertically beyond the spike only in the first direction, and the second sidewall portion extends vertically beyond the spike in the first and second directions.
 30. The assembly of claim 21, wherein the spike provides an abrupt discontinuity between the first and second sidewall portions.
 31. The assembly of claim 21, wherein the first distance is at most four times the second distance.
 32. The assembly of claim 21, wherein the first distance is about two times the second distance.
 33. The assembly of claim 21, wherein the insulative base is laterally aligned with the metal pillar at a surface that faces in the second direction.
 34. The assembly of claim 21, wherein the insulative base extends vertically beyond the metal pillar in the second direction.
 35. The assembly of claim 21, wherein the assembly is a first-level package.
 36. A semiconductor chip assembly, comprising: a semiconductor chip that includes first and second opposing surfaces, wherein the first surface of the chip includes a conductive pad; a conductive trace that includes a routing line and a metal pillar, wherein the metal pillar is copper and includes first and second opposing surfaces and tapered sidewalls therebetween, the first surface of the metal pillar faces in a first direction and contacts and is non-integral with the routing line, the second surface of the metal pillar faces in a second direction opposite the first direction and is spaced from the routing line, the second surface of the metal pillar is flat and parallel to the first and second surfaces of the chip, a surface area of the second surface of the metal pillar is disposed within a surface area of the first surface of the metal pillar, the surface area of the first surface of the metal pillar is at least 20 percent larger than the surface area of the second surface of the metal pillar, the tapered sidewalls include first and second sidewall portions that are adjacent to one another at a spike in the metal pillar, the first sidewall portion is a continuous concave arc that is adjacent to the first surface of the metal pillar, is spaced from the second surface of the metal pillar, slants inwardly towards the second surface of the metal pillar, extends vertically beyond the second sidewall portion in the first direction, and has a maximum diameter at the first surface of the metal pillar and a minimum diameter at the spike, the second sidewall portion is a continuous concave arc that is adjacent to the second surface of the metal pillar, is spaced from the first surface of the metal pillar, slants inwardly towards the second surface of the metal pillar, extends vertically beyond the first sidewall portion in the second direction, and has a maximum diameter at the spike and a minimum diameter at the second surface of the metal pillar, the spike protrudes laterally from and spans 360 degrees laterally around the metal pillar, is spaced from the first and second surfaces of the metal pillar, and is a first distance in the first direction from the first surface of the metal pillar and a second distance in the second direction from the second surface of the metal pillar, and the first distance is greater than and at most four times the second distance; a connection joint that electrically connects the routing line and the pad; an encapsulant; and an insulative base, wherein the chip is embedded in the encapsulant and extends vertically beyond the routing line, the metal pillar and the insulative base in the first direction, the routing line extends laterally beyond the metal pillar towards the chip, extends vertically beyond the metal pillar in the first direction and extends vertically beyond the chip in the second direction, the metal pillar is embedded in the insulative base, is disposed outside a periphery of the chip, extends vertically beyond the chip, the routing line, the connection joint and the encapsulant in the second direction, does not cover the routing line in the second direction and is not covered in the second direction by the encapsulant, the insulative base or any other insulative material of the assembly, the encapsulant contacts the chip and extends vertically beyond the chip, the routing line, the metal pillar, the connection joint and the insulative base in the first direction, and the insulative base contacts the routing line and the metal pillar, is overlapped by the chip, extends vertically beyond the chip, the routing line, the connection joint and the encapsulant in the second direction and extends vertically at least as far as the metal pillar in the second direction.
 37. The assembly of claim 36, wherein the metal pillar has a generally conical shape with a diameter that substantially continuously decreases from the first surface of the metal pillar to the second surface of the metal pillar.
 38. The assembly of claim 36, wherein the first sidewall portion extends vertically beyond the spike only in the first direction, and the second sidewall portion extends vertically beyond the spike only in the second direction.
 39. The assembly of claim 36, wherein the spike provides an abrupt discontinuity between the first and second sidewall portions.
 40. The assembly of claim 36, wherein the assembly is a first-level package. 